Android Police points to a Samsung support forum thread in which people report getting weaker signals on multiple carriers, though it says that Sprint reports outnumber those on AT&T and T-Mobile. The site also says that in its own tests, even the way you hold the phone and whether or not it's in a case can impact the signal.
A smattering of people have isolated the problem to the use of a weaker signal band, at least on Sprint. Android Police points to a Samsung forum post that says disabling Band 41 and Band 25 will resolve the problem for now while waiting on a permanent fix.
Android Police goes on to say that its own experiences seem to depend on location and band frequency, and T-Mobilers or AT&Ters on Band 12 had more problems than on T-Mobile with Band 2. The most reports come from S10 Plus owners.
Samsung didn't immediately reply to a request for comment.