A Study of Multiple Immunotherapy-Based Treatment Combinations in Patients With Locally Advanced Unresectable or Metastatic Gastric or Gastroesophageal Junction Cancer (G/GEJ) or Esophageal Cancer (Morpheus-Gastric and Esophageal Cancer)

5-FU 2400 milligrams per square meter (mg/m\^2) by continuous intravenous (IV) infusion over 46 hours on Days 1 and 2 and Days 15 and 16 of every 28-day cycle.

Leucovorin: 100 mg/m\^2 IV over 2 hours on Days 1 and 15 of every 28-day cycle.

Oxaliplatin: 100 mg/m\^2 administered by IV infusion over 2 hours on Days 1 and 15 of every 28-day cycle.

Atezolizumab: 840 mg by IV infusion on Days 1 and 15 of every 28-day cycle.

Cobimetinib: 60 mg by mouth once a day on Days 1-21 of every 28-day cycle

Ramucirumab: 8 mg/kg administered by IV infusion over 60 minutes on Days 1 and 15 of every 28-day cycle.

Paclitaxel: 80 mg/m\^2 administered by IV infusion on Days 1, 8, and 15 of every 28-day cycle.

PEGPH20: 3 micrograms per kilogram (mcg/kg) administered by IV infusion on Days 1, 8, and 15 of every 21-day cycle.

BL-8040: 1.25 mg/kg administered by subcutaneous (SC) injection on Days 1-5 during the 5-day priming period prior to Cycle 1; 1.25 mg/kg administered by SC injection three times a week (Days 1, 3, 5, 8, 10, 12, 15, 17, and 19 of every 21-day cycle).

Linagliptin: 5 mg orally once a day of every 21-day cycle.

Atezolizumab: 1200 mg administered by IV infusion on Day 1 of every 21-day cycle

Cobimetinib: 40 or 60 mg (depending on the recommended dose determined during the safety run-in phase) by mouth once a day on Days 1-21 of every 28-day cycle.

Cisplatin: 80 mg/m\^2 administered by IV infusion on Day 1 of each 21 day cycle. Treatment will be capped after 6 doses.

Tiragolumab: 600 mg administered by IV infusion on Day 1 of every 21 day cycle.

5-FU 800 mg/m\^2 administerd by IV infusion on Days 1-5 of each 21 day cycle.