Hi,
Has the ML-2166W been working under Big Sur earlier? Any information about the exact driver version used/reinstalled?
Would it be correct to assume that you had tried to reset the printing system in accordance with the following article?
Reset the Mac printing system to solve a problem - Apple Support
Add a printer on Mac - Apple Support
There is a (Feb 11, 2021) Samsung Universal Print Driver V3.93.01 for Big Sur from HP (https://ftp.hp.com/pub/softlib/software13/printers/SS/Print_Common_SW/Samsung_Mac_Driver_V3.93.01.dmg). See also the HP article https://support.hp.com/us-en/document/c06520117 (for Catalina, but should largely apply to Big Sur). No direct information about an ML-2166W. There is an ML-2161, though. You could perhaps carry out experiments based on information in the article about the ML-2161 (with references to the compatible models using UPD).
Software conflicts cannot be ruled out when testing drivers. Make sure that you have backup copies of all important files before doing anything. It may be a good idea to reset the printing system between tests.