Samsung needs to add an option to the settings to decide what network the device recognizes similar to that "fruit" company device manufacturer. When there are issues with 5G service the device will get "network timed out" errors on most apps but when in LTE it works fine. The frustrating part is that the device seems to be functioning fine and the user would seemingly not notice and immediately think it is a device issue . This is remidied in other devices by selecting "LTE" instead of 5G in the settings of the device. Currently this is not an option in the setting in a Samsung device. Simple thing that should be in the settings already. I'm surprised Samsung didn't add this with 5G capability. Please add the ability to select the network of preference!
You do not mention which model of S20 you have.
Is it one of the U.S.A. carrier minority variants?
On the global models you can go to... Settings > Connections > Mobile networks > Network mode... for each of the SIMs and select which network configuration you want (see screenshot)
That is the reason as the U.S.A. single SIM, carrier minority variants run their own carrier's heavily adapted ersatz version of Samsung's stock worldwide firmware, that has lots of stock features removed/amended by the U.S. carriers to suit their needs.
You will need to complain to your U.S.A. carriers as they dictate and control their own carrier firmwares on most phone manufacturers devices.
You have it the wrong way around... Apple would not allow it on the iPhone. In the U.S.A; Apple calls the tune whilst other phone manufacturers must acquiesce to U.S. carriers demands if they wish to market their phones in the States. This is why I stated in my previous post... "they dictate and control their own carrier firmwares on most phone manufacturers devices"