All older printers are not working in macOS v11 (Big Sur) Equipment: Brother MFC-8890DW and Brother MFC-9320CW
I suspect it will work on: All older printers with Big Sur!
On upgrade to Big Sur, I found that my 8-year old expensive Brother MFC printers would no longer work, and that Apple was recommending that we use AirPrint. I could install the printers using macOS v10.15 (Catalina) (or older) drivers, and my scanners would work, but not the printers! AirPrint would not work either.
I scoured the web for many hours and tried 1) Resetting the printer system - no go.  2) Reinstalling CUPS (with SIP disabled and Gatekeeper disabled - no go because of Apple's read-only /usr filesystem ... not getting into setting up remounting the root (/) filesystem because of FileVault problems.
I noticed that this was a problem that everyone was having regardless of their printer brand - indicating that it was a system problem.
What worked: I read the error logs on my printers. They pointed me to permission problems with /usr/libexec/cups. Perms should be 755.
To make this work:

System Integrity Protection should be disabled.
You must be a sudoer or have root permissions.

Instructions
Open a terminal.

cd to /usr/libexec
sudo chmod -R 755 cups

That's it! Printing with older drivers works now! AirPrint works. The scanners work. Apparently Apple screwed up the perms on the cups directory that makes printing work when they created their protected filesystem! Urrgghh! This should work with all older printers regardless of brand.
YMMV.