Changing Network Mode Galaxy S20 Ultra 5G

2G networks are going to be shutdown soon in the few places they are available and the 3G network sunset for all US carriers was last year.  In some rare spots, there still might be 3G available where no other coverage exists but those spots will eventually be upgraded.  Even Canadian carriers are sunsetting their 3G networks next year. 

On my s23 Ultra, I can turn off 2G and 5G within the standard menu but other options require access to some of the Engineering menus.  Doing so can prevent your device from accessing cellular networks if you do not know what you are doing.  If you want to learn on how to do so.  Check out the Samsung s20 subforum on the XDA Forum.