Testing the Combination of Venetoclax and Rituximab, in Comparison to the Usual Treatment (Ibrutinib Plus Rituximab or Zanubrutinib Alone) for Waldenstrom's Macroglobulinemia/Lymphoplasmacytic Lymphoma

Inclusion Criteria: * Participants must have had a confirmed diagnosis of Waldenstrom's macroglobulinemia (WM)/lymphoplasmacytic lymphoma (LPL). Participants must have measurable disease as determined by IgM protein quantification. * IgM Spike: ≥ 500 mg/dL (≥ 5 g/L) * Extramedullary disease: The manifestation of a lymphoid mass outside of the bone marrow, resulting in enlargement in extramedullary organs such as the lymph nodes or spleen. Note: all participants must have measurable IgM spike, but are not required to have extramedullary disease * Testing to establish baseline disease status must be performed within 28 days prior to registration * Participants must have at least one of the criteria to require therapy for WM including: * Anemia * Thrombocytopenia * Neuropathy related to WM * Symptomatic hyperviscosity or serum viscosity levels ≥ 4.0 centipoises * WM associated glomerulonephritis or renal disease, bulky disease, or constitutional symptoms * Constitutional symptoms can be described as: * Unintentional weight loss \>= 10% within the previous 6 months prior to screening * Fevers higher than 100.5 degrees Fahrenheit (F) or 38.0 degrees Celsius (C) for 2 or more weeks prior to screening without evidence of infection * Night sweats for more than 1 month prior to screening without evidence of infection * Clinically relevant fatigue which is not relieved by rest due to WM * Participants who require ongoing use or received a …