It's actually a box you need to check in settings >
System Preferences > Apple ID > iCloud > "Apps on this Mac using iCloud: "
(under your icon/email/overview/name/pass/payment/
iCloud on the left panel in the Apple Id icon you click on in the top right next to family sharing.)
Scroll down and verify these are checked:
[ ] Keychain <-----------------------CHECK THIS BOX***** Enjoy your digital life again :)
[ ] Find My Mac <------------- You are setting it up, so arguably you already found it... but I digress.
So... Enable these, log in with your password, it may not function until logging in and out - some message or error might be there if logging in for the first time and not getting the authentication verified upon initialization, but this was the place to look in Big Sur for restoring saved passwords and logins, payment and card info and I looked everywhere but here to find it.
Seems like it would be in Security and Privacy, or in Safari under saved passwords - that would link you to here... and remind you to turn on find my mac.. but it doesn't - and apple support was decently helpful during business hours to identify this.
Again, my two cents, hope it helps someone out there in a similar boat/bind/quandry/ digital abyss.
Stay safe out there during these dark times!