Login Screen

it definitely does depend on a single user setup.

the easy way is if you are the sole user (not even a guest account) AND file vault is turned off you can go to System Preferences > Users & Groups > Login Options and set "Display login window as" to "List of users". then your login screen matches your desktop background.

if you are using file vault or have multiple users, the above will not work.  if that's your situation, you will need to wait for apple to address this. it may be worth your time to send feedback directly to apple. Feedback - macOS - Apple. 

Seems to depend if you are the only user. See:

https://discussions.apple.com/thread/253314107

Can I change login screen with OS Monterey

thank you. :) apparently apple agrees with me too. https://discussions.apple.com/thread/253382773

+ 1 there

+ 1 + 1 there

Almost there too