ugh, I edited this because I had typed the wrong code.
it's *#2263# ( *#BAND# )
I have a Samsung s22+
SM-S906U1 factory unlocked, with updates thru jan 1 2023 including the infamous update of july '22 that sabotaged access to the hiddennetwork activity band selection.
The *#73# dialer code does not work on this phone.
Also, note that which dialer codes do and do not work depends on what phone app you're using to dial with.
Using the original Samsung phone app, not updated, that came installed on this phone
*#2263#
Directly opens ServiceMode band selection menu.
Using a different phone app, like Google Phone the code doesn't work. I recommend if *#2263# is not working on your carrier branded phone to install an apk of the Samsung phone app from a factory unlocked version to see if the dialer code works. This app has permissions to run this ServiceMode menu, but trying to launch the same activity with another app returns an error of "permission denied"
I hope this helps