1. At least 18 years of age, inclusive 2. Subject (or their legally acceptable representative) must sign an ICF indicating that he or she understands the purpose of and procedures required for the trial and are willing to participate in the trial prior to any other trial related assessments or procedures. Where required by local or country specific regulations, each subject must sign a separate informed consent form if he or she agrees to provide samples for genomic biomarker analysis (DNA and RNA). If a subject refuses to consent to DNA and RNA research in these specific regions, the subject is still eligible to participate in the trial. 3. ECOG PS score of 0 or 1 (see Appendix 7) 4. CD20-positive NHL at most recent (previous or current) representative tumor biopsy based on the pathology report 5. Measurable disease defined as e"1 measurable nodal lesion (long axis >1.5 cm and short axis >1.0 cm) or e"1 measurable extra-nodal lesion (long axis >1.0 cm) on CT or MRI 6. Acceptable organ function at screening defined as: a. ANC e"1.0 × 109/L (growth factor use is allowed) b. Platelet count >75 x 109/L, or e"50 x 109/L if bone marrow infiltration or splenomegaly c. ALT level d"2.5 times the ULN d. Total bilirubin level d"2 × ULN e. EGFR >50 mL/min (by Cockcroft-Gault Formula, see Appendix 4) f. PT, INR, and aPTT d" 1.5 x ULN, unless receiving anticoagulant 7. Before enrollment, a woman must be either: a. Not of childbearing potential: postmenopausal (>45 years of age with amenorrhea for at least 12 months or any age with amenorrhea for at least 6 months and a serum FSH level >40 IU/L or mIU/mL]), permanently sterilized (eg, bilateral tubal occlusion (which includes tubal ligation procedures as consistent with local regulations), hysterectomy, bilateral salpingectomy, bilateral oophorectomy), or otherwise be incapable of pregnancy. Of childbearing potential and practicing a highly effective method of birth control consistent with local regulations regarding the use of birth control methods for subjects participating in clinical trials: eg, established use of oral, injected or implanted hormonal methods of contraception, placement of an IUD or IUS, barrier methods: condom with spermicidal foam/gel/film/cream/suppository or occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/suppository, male partner sterilization (the vasectomized partner should be the sole partner for that subject), true abstinence (when this is in line with the preferred and usual lifestyle of the subject) during the trial and for 12 months after receiving the last dose of epcoritamab (see additional criteria for Arm 2). See Appendix 13 for additional details. Note: If the childbearing potential changes after start of the trial (eg, woman who is not heterosexually active becomes active, premenarchal woman experiences menarche) a woman must begin a highly effective method of birth control, as described above. 8. A woman of childbearing potential must have a negative serum (beta-hCG) pregnancy test at screening and a negative urine pregnancy test before treatment administration on Day 1 of Cycle 1 (see additional criteria for Arm 2) 9. A woman must agree not to donate eggs (ova, oocytes) for the purposes of assisted reproduction during the trial and for 12 months after receiving the last dose of epcoritamab 10. A man who is sexually active with a woman of childbearing potential and has not had a vasectomy must agree to use a barrier method of birth control, eg, either condom with spermicidal foam/gel/film/cream/suppository or partner with occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/suppository, and all men must also not donate sperm during the trial and for 12 months after receiving the last dose of epcoritamab (see additional criteria for Arm 2) 11. Subjects must agree not to donate blood for 60 days after receiving the last dose of trial treatment 12. Subject must be willing and able to adhere to the prohibitions and restrictions specified in this protocol 5.1.1 Inclusion Criteria Specific to Arm 1 (Epcoritamab + R-CHOP) 13. Documented DLBCL (de novo or histologically transformed) according to the 2016 WHO classification 14. Newly diagnosed, previously untreated DLBCL 15. International Prognostic Index score e"3 16. No prior therapy for the lymphoma other than corticosteroids not exceeding threshold listed in exclusion criterion 5 17. Eligible to receive R-CHOP per investigator determination. Investigators to confirm that subjects who are e"80 years old are eligible to receive R-CHOP according to the protocol, without preplanned dose reductions 18. LVEF within institutional normal limits by MUGA or echocardiography at screening 5.1.2 Inclusion Criteria Specific to Arm 2 (Epcoritamab + R2) 19. Histologically confirmed CD20+ FL according to the WHO 2016 classification 20. R/R FL, grade 1, 2 or 3a, stage II, III, or IV 21. Previously treated with at least 1 prior anti-neoplastic agent, including anti-CD20 antibody 22. Must have a need for treatment initiation based on symptoms and/or disease burden 23. Eligible to receive R2 per investigator determination 24. Females of childbearing potential must use 2 forms of contraception consistent with local regulations regarding the use of birth control methods for subjects receiving lenalidomide or continuously abstain from heterosexual sex during the following time periods related to this trial: 1) for at least 28 days before starting trial drug, 2) while participating in the trial, and 3) for at least 12 months after discontinuation from the trial, see Appendix 14, Lenalidomide Pregnancy Risk Minimization Plan. 25. A woman of childbearing potential must have a negative serum (beta-hCG) pregnancy test at screening (within 10-14 days of Day 1 of Cycle 1) and a negative urine pregnancy test within 24 hours of dosing on Day 1 of Cycle before treatment administration 26. Males must always use a latex or synthetic condom during any sexual contact with females of reproductive potential while taking lenalidomide and for up to 4 weeks after discontinuing lenalidomide, even if they have undergone a successful vasectomy. Male subjects taking lenalidomide must not donate sperm. See Appendix 14, Lenalidomide Pregnancy Risk Minimization Plan. 5.1.3 Inclusion Criteria Specific to Arm 3 (Epcoritamab + BR) 27. Histologically confirmed CD20+ FL according to the WHO 2016 classification. 28. Newly diagnosed, previously untreated FL grade 1, 2, or 3a, stage II, III, or IV 29. No prior therapy for the lymphoma other than corticosteroids not exceeding threshold listed in exclusion criterion 5 30. Must have a need for treatment initiation based on symptoms and/or disease burden 31. Eligible to receive BR per investigator determination 5.1.4 Inclusion Criteria Specific to Arm 4 (Epcoritamab + R-DHAP) 32. Documented DLBCL (de novo or histologically transformed) according to the 2016 WHO classification 33. Relapsed or refractory to prior therapy 34. Eligible for HDT-ASCT 35. Eligible to receive R-DHAP per investigator determination 5.1.5 Inclusion Criteria Specific to Arm 5 (Epcoritamab + GemOx) 36. Documented DLBCL (de novo or histologically transformed) according to the 2016 WHO classification 37. Relapsed or refractory to prior therapy 38. Ineligible for HDT-ASCT due to age, PS, or comorbidity 39. Eligible to receive GemOx per investigator determination

5.2 Exclusion Criteria (Arms 1, 2, 3, 4, and 5) Any potential subject who meets any of the following criteria will be excluded from participating in the trial. 1. History of severe allergic or anaphylactic reactions to anti-CD20 mAb therapy or known allergy or intolerance to any component or excipient of epcoritamab 2. Chemotherapy, radiation therapy, or major surgery within 4 weeks prior to the first dose of epcoritamab 3. Treatment with an anti-cancer antibody or an investigational drug within 4 weeks or 5 half-lives, whichever is shorter, prior to the first dose of epcoritamab 4. Treatment with CAR-T therapy within 30 days prior to first dose of epcoritamab 5. Cumulative dose of corticosteroids more than the equivalent of e" 140 mg of prednisone within 2-week period before the first dose of epcoritamab 6. Vaccination with live vaccines within 28 days prior to the first dose of epcoritamab 7. Clinically significant cardiac disease, including: a. Myocardial infarction within 1 year prior to the first dose of epcoritamab, or unstable or uncontrolled disease/condition related to or affecting cardiac function (eg, unstable angina, congestive heart failure, New York Heart Association Class III-IV, see Appendix 5), cardiac arrhythmia (CTCAE Version 4 Grade 2 or higher), or clinically significant ECG abnormalities b. Screening 12-lead ECG showing a baseline QTcF >470 msec 8. Evidence of significant, uncontrolled concomitant diseases that could affect compliance with the protocol or interpretation of results 9. Known active bacterial, viral, fungal, mycobacterial, parasitic, or other infection (excluding fungal infections of nail beds) at trial enrollment or significant infections within 2 weeks prior to the first dose of epcoritamab 10. CNS lymphoma or known CNS involvement by lymphoma at screening as confirmed by MRI/CT scan of the brain and, if clinically indicated, by lumbar puncture 11. Active positive tests for hepatitis B virus or hepatitis C virus indicating acute or chronic infection 12. History of HIV antibody positivity, or tests positive for HIV at screening 13. Positive test results for HTLV-1 14. Suspected active or latent tuberculosis 15. Known past or current malignancy other than inclusion diagnosis, except for: a. Cervical carcinoma of Stage 1B or less b. Non-invasive basal cell or squamous cell skin carcinoma c. Non-invasive, superficial bladder cancer d. Prostate cancer with a current PSA level < 0.1 ng/mL e. Any curable cancer with a CR of > 2 years duration 16. Neuropathy >grade 1 17. Female who is pregnant, breast-feeding, or planning to become pregnant while enrolled in this trial or within 12 months after the last dose of epcoritamab 18. Male who plans to father a child while enrolled in this trial or within 12 months after the last dose of epcoritamab 19. Subject has any condition for which, in the opinion of the investigator, participation would not be in the best interest of the subject (eg, compromise the well-being) or that could prevent, limit, or confound the protocol-specified assessments. 5.2.1 Exclusion Criteria Specific to Arm 1 (Epcoritamab + R-CHOP) 20. Prior therapy for DLBCL with the exception of nodal biopsy 21. Contraindication to any of the individual drugs of the R-CHOP regimen 5.2.2 Exclusion Criteria Specific to Arm 2 (Epcoritamab + R2) 22. FL Grade 3b 23. Histologic evidence of transformation to an aggressive lymphoma 24. Contraindication to rituximab or lenalidomide 25. Prior allogeneic HSCT 26. Autologous HSCT within 3 months of the first dose of epcoritamab 27. Unwilling or unable to take aspirin prophylaxis (subjects with low or intermediate risk for thromboembolism) or prophylactic anticoagulant (if high risk for a thromboembolic event) 5.2.3 Exclusion Criteria Specific to Arm 3 (Epcoritamab + BR) 28. FL grade 3b 29. Histologic evidence of transformation to an aggressive lymphoma 30. Prior therapy for FL with the exception of nodal biopsy 31. Contraindication to bendamustine or rituximab 5.2.4 Exclusion Criteria Specific to Arm 4 (Epcoritamab + R-DHAP) 32. Contraindication to any of the individual drugs of the R-DHAP regimen 5.2.5 Exclusion Criteria Specific to Arm 5 (Epcoritamab + GemOx) 33. Contraindication to any of the individual drugs of the GemOx regimen