Testing the Addition of AZD6738 (Ceralasertib) to Immunotherapy to Increase Time Without Cancer for Patients With Non-Small Cell Lung Cancer

Inclusion Criteria: * STEP 0: Patient must be \>= 18 years of age * STEP 0: Patient must have stage II to select stage IIIB (N2 but excluding N3) non-small cell lung cancer (NSCLC) of any histology using International Association for the Study of Lung Cancer (IASLC) 8th edition. Stage is assessed at time of initiating pre-operative chemo-immunotherapy * STEP 0: Patient must fall into one of the following categories: * Planning to undergo, be currently undergoing, or recently completed any standard of care neoadjuvant chemo-immunotherapy with plans to undergo surgical resection * Recently completed any standard of care neoadjuvant chemo-immunotherapy AND completed surgical resection and are awaiting pCR status. * Recently completed any standard of care neoadjuvant chemo-immunotherapy AND completed surgical resection with confirmed non-path complete response (CR) status. NOTES: * Patient must have completed at least 3 cycles of neoadjuvant chemo-immunotherapy before surgery in order to be eligible for Step 1 randomization. * Patients who have completed their surgical resection prior to enrollment in step 0 registration must have their surgery date within a window that will allow initiation of EA5231 treatment (cycle 1 day 1) to commence within 4-12 weeks following surgery * STEP 1: EA5231 CLEAR randomization for patients without a pCR post-surgery. Patient's with pCR after surgery will be offered to enroll in the SWOG study S2414 INSIGHT instead * STEP 1: Patient…