Wtf? LTE off switch is nowhere?

AT&T shut down their 3G network on 2/22/22. AT&T has always played a game where they called a slightly enhanced version of the older network by a name that made you think it was the newer one. What AT&T called "4G" was really not. No other carrier used both terms. Once the 3G network went away, so did "4G". You are now left with the actual 4G service which is called "LTE".

Having the switch would be pointless as there is no 3G network for you to switch to.

The carrier is in charge of that whether or not that switch is available for your service. Who is your carrier? If your carrier has shut down its 3G network, that switch is superfluous.