Thank you! This solved the issue on our "Family Mac" which is a 16-inch MBP 2019 (Intel i7) running Tahoe 26.2, with file vault enabled. We have 4 family members each with an own account, two of which are admins. Fast user switching via the menu bar always worked flawlessly. User selection in the login screen after logging out also worked correctly. However, when one of us was logged in and locked the screen via Ctrl-Cmd-Q or by closing the lid, only the same person could re-login, but no other user could be selected in the lock screen (clicking on the "avatar" of the logged-in user who had locked the screen did not show any other users). Now, after entering the above terminal command, the user selection in the lock screen works as expected, which is what we need, and this is how it should have worked in the first place. Imagine a situation where I have gone to work after locking the screen, and any of the children or my wife needs the MacBook in the afternoon - there was no way to access their accounts.
This non-availability of user switching in the lock screen (without entering the above sudo terminal command once) is what I would call a bug in Tahoe. Should be easy to fix by Apple.