Study of GS-0189 (Formerly FSI-189) as Monotherapy and in Combination With Rituximab in Participants With Relapsed/Refractory Non-Hodgkin Lymphoma

Key Inclusion Criteria: * DLBCL, follicular lymphoma (FL), mantle cell lymphoma (MCL), or marginal zone lymphoma (MZL) relapsed/refractory (R/R) to at least 2 prior lines of therapy. Prior autologous hematopoietic cell transplantation and individuals with transformed lymphomas are permitted. Individuals must be at least 3 months out from prior autologous hematopoietic cell transplantation. Individuals with indolent lymphomas must be candidates for systemic treatment in the judgment of the treating physician. * In the DLBCL Expansion part: DLBCL that is relapsed or refractory to at least 2 prior lines of therapy. Prior autologous hematopoietic cell transplantation and individuals with transformed lymphomas are permitted. * Eastern Cooperative Oncology Group (ECOG) score of 0 to 2. * For the DLBCL expansion cohort, disease must be measurable for response per Lugano criteria. For all other cohorts, disease must be measurable or assessable for response per Lugano criteria. * Exhibit acceptable hematopoietic, liver, renal, and coagulation function as assessed by laboratory tests. Key Exclusion Criteria: * Individuals with active brain metastases (Individuals with stable treated central nervous system (CNS) lesions who are off corticosteroid therapy for at least 3 weeks are not considered active. * Individuals with Burkitt's lymphoma. * Prior treatment with a chimeric antigen receptor (CAR) T-cell therapy ≤ 90 days from first dose of study drug. * Prior allogeneic stem cell transplant. * Previous anticancer therapy including chemotherapy, hormonal therapy, and investigational agents within 3 weeks or at least 4 half-lives (up to a maximum of 4 weeks), whichever is longer, prior to first dose of study drug. * Known active or chronic hepatitis B or C infection or human immunodeficiency virus. * Prior treatment with CD47 or signal regulatory protein alpha (SIRPα)-targeting agents. * Hypersensitivity to the active substance, to murine proteins, or to any of the other excipients of rituximab * Significant medical diseases or conditions, as assessed by the Investigator and Sponsor, that would substantially increase the risk:benefit ratio of participating in the study. * Rituximab-containing cohorts only: Receipt of live/attenuated vaccines within 30 days of rituximab dosing * Has persisting toxicity related to prior therapy of Grade \> 1 in severity per National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE), Version 5.0. Note: Other protocol defined Inclusion/Exclusion criteria may apply.