Options under the "cellular" menu are controlled by the carrier, not by Apple.
For example, AT&T removed the option to shut off LTE and have phones drop back to 4G as part of their work to decommission their 3G networks later this year.
This is because on AT&T, when your annunciator reads "5G E" it's really "5G Evolution" which is really LTE plus some 5G extensions.
When your annunciator reads "LTE" it's actually 4G + LTE extensions, and when it says "4G" it's really 3G + some 4G features.
AT&T did this for their own marketing reasons, but the bottom line is that you can't "shut off" LTE any more because that would in reality drop you to their "3G + 4G extensions" network, and the AT&T 3G network is scheduled to be shut down on February 22, 2022.
After February 22, 2022 some 4G LTE modules and devices that request 3G voice services and data-only services to connect to the AT&T network will no longer work. You don't want to be left without service.
https://www.business.att.com/explore/make-the-switch.html
After that any networks that currently show "4G" on your phone will simply no longer exist on AT&T, there will only be LTE, 5G E, 5G and 5G+.
Status icons and symbols on your iPhone - Apple Support