Cool video detailing what the 'Developer Options' menu items do, and has tips for sending feedback regarding Beta 12 to the developers.
* options in video are for a Google phone, but they're the same thing as in the S21 bar slightly different wording in a couple.
For those who don't know how to activate the 'Developer Options' menu on your S21...
Settings-About Phone-Software Information-
...then tap on 'Build Number' 7 times/until a window appears stating 'Developer Mode Enabled'.
*I wouldn't mess with them if you don't know what you're doing; some of them are handy though, and the attached video does a good job of describing their functions, so you'll know what you can enable/disable.