FYI re Lexmark printers and Big Sur
Lexmark has acknowledged that their drivers do not work with Big Sur:
However, it appears that Lexmark has since provided updated drivers:
Universal color printer driver:
https://downloads.lexmark.com/downloads/drivers/Lexmark_UC1_PrinterSoftware_12072020.dmg
Universal mono (black and white) printer driver:
https://downloads.lexmark.com/downloads/drivers/Lexmark_UM1_PrinterSoftware_12012020.dmg
I can confirm that this works for my C792de printer, and supports all features, including stapling and double-sided printing. The only thing that's different is the icon does not match the printer, but that can is relatively easily fixed.