I'm experiencing this as well on my A71, when I was on Android 10 by phone would loss just 1% overnight if even that. Now on Android 11 I loss as much as 12% overnight & nothing I've tried resolved the issue.
Not of these worked, even if I power off the phone overnight it seems to still loss about 3%. Device Care battery statistics doesn't seem to show what's causing this drain.
On a side note.....I don't like the new power saving mode on Android 11, it sucks compared to the previous one from Android 10. This seems like its a system problem that Samsung should fix, should have known something was up when I got the update early, I never agreed to be a beta tester!