I don't have the "play sound on start up" preferences

for whatever reason, apple removed that option from catalina. you should be able to reactivate / deactivate the chime with terminal commands.

to turn it on, open terminal (in Applications>Utilities) and paste this command into terminal (without the quote marks):

"sudo nvram StartupMute=%00"

enter your admin password when prompted. then restart the mac to test.

to turn it off, again open terminal and paste this command into terminal (without the quote marks):

"sudo nvram StartupMute=%01"

enter your admin password when prompted. then restart the mac to test.

You need Big Sur 11.0 or later.