I have solid 5G service around my entire service (including inside my apartment) but since getting the beta update my signal icon drops to 4G or "loses" signal completely yet my phone still works like it's connected to 5G (speed test confirmed), makes HD phone calls, apps work fine, browsing works fine. Just adding my own experience hoping that it helps identify the issue.
I have the S20 Ultra 5G. Unlocked in the U.S. on T-Mobile and I have no issues. I'm connected to 5G 100% of the time with a great signal. calls, text all work just fine. latest beta
I also have the s20 ultra unlocked on Verizon 5g and have not had any issues with the beta, but I have noticed that some people have not been able to connect to a 5g network ,most people have been able to fix the issue by turning off their phones and then pulling out the Sim card or about a minute then after reinstalling the Sim card turn on phone and then turn on airplane mode for a few minutes then connection issues seem to work, please generate a error report and send it to the beta moderator