A Study to Learn How Safe and How Well Linvoseltamab Works Compared to Standard Treatment in Adult Patients With Multiple Myeloma Who Are Not Eligible for Transplant

Inclusion Criteria: 1. Participants must have confirmed diagnosis of symptomatic MM per IMWG criteria. 2. Participants must not be considered a candidate for high-dose chemotherapy (HDT) and ASCT, as described in the protocol. 3. Participants must have measurable disease as defined in the protocol. 4. Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2. 5. Participants must have clinical laboratory values within a prespecified range. Exclusion Criteria: 1. International Myeloma Working Group Frailty Index of 2 with the exception of participants who have a score of 2 based on age alone. 2. Participants who defer transplant due to personal preference. 3. Participants with non-secretory MM, active plasma cell leukemia, known light-chain (AL) amyloidosis in the presence of a concurrent diagnosis of myeloma, any other form of amyloidosis, Waldenström macroglobulinemia, or known POEMS syndrome. 4. Any prior therapy for monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), or MM, with the exception of: * focal radiation and/or * a short course of corticosteroids as defined in the protocol. 5. Participants who have received or are receiving any investigational agent or cell therapy with known or suspected activity against MM 6. Participants who have known central nervous system (CNS) or meningeal involvement with MM or known or suspected progressive multifocal leukoencephalopathy (PML), a history of a neurocognitive condition or CNS movement disorder, OR a history of seizure, transient ischemic attack (TIA), stroke or seizure within 12 months prior to study C1D1. 7. Participants who have uncontrolled intercurrent illness. 8. Known contraindications to the use of daratumumab or lenalidomide per local prescribing information. 9. History of allogeneic hematopoietic stem cell transplantation or solid organ transplant at any time. NOTE Other protocol defined inclusion/exclusion criteria apply.