To test that, forget about all the fancy apps and just check the basic GNSS output to see whether you get a fix e.g. New Post: November Librem 5 update: Byzantium Released - #36 by irvinewade
It can take a long time (e.g. 20 minutes) outside to get your first fix but thereafter it should be quick - or you may indeed have poor connection on the antenna - but best to eliminate other possible issues first.
The other thing to confirm is that, assuming you are using geoclue as the source of location information for the applications, you have configured geoclue to use only the GNSS as the underlying source. You need this anyway for any kind of sane troubleshooting, but you also really really don’t want geoclue using e.g. WiFi for location information (since that involves leaking information, including your location, to the online service that maps WiFi MAC addresses to physical locations) and e.g. most people wouldn’t want it using mobile tower for location information (since that is not very accurate).