You used to be able to use the ##4636## trick to get a hidden menu, but now that’s gone too. There’s nothing in the menu that alllows you to select which network to use. I hate to keep having network disconnects and in perpetual 4G/5G back and forth and battery draining.
I use Samsung btw
Edit: For context: Its due to issues with being near the edge of the 5G zone so your phone keeps going back and forth between 4G and 5G which (I suspect), is what causes constant network disconnection, phone being hot/warm, and battery drain. Very annoying.
Not a samsung, but I have this option:
“Settings” > “Network & internet” > “SIMs” > <select SIM> > “Preferred network type”
Selecting anything less than 5G will cap it at that level.
5G seems to work fine for me while I’m at home, but it absolutely sucks for mobile use.