PSA REGARDING DOWNGRADING /ROLLBACK /FLASHING WITH ODIN:
First of all, be advised that flashing will probably void any warranty you may have (though it's better than being stuck with a 90% useless device). Second, for most folks with S21's (can't speak for other models), flashing is not an option. 😭
The problem is that for S21's, the version/bit number for the firmware rolled over to a new binary series after the 6.1 update (A--->B). Downgrading requires you to stay within the same version number. Otherwise you will trigger Knox and brick your phone (zero chance of restoration). So make sure to check your firmware number before you get your hopes up and waste your time (like I did).
Aside from that, the flashing process is actually pretty straightforward (there are lots of videos out there on how to do it). I sure envy the people who have the option to rollback their devices.... Samsung has really stranded the rest of us up s**t creek with no paddle. ☹️
