npub13dg3q4swwjtjgj824veaxlvhmlhdk3g93rv00peawn230g0jd6eqlgejem (npub13dg…ejem) The minimum required RAM for EL7 is 1 GB, and for EL8/9 it's 1.5 GB, so yeah I'd expect only using 0.5 GB will eventually bite you in the rear. Getting OOMs during a leapp upgrade definitely sounds like the worst possible time for that biting to happen.
https://access.redhat.com/articles/rhel-limits#minimum-required-memory-3