Not counting early revisions which indeed had poor GNSS reception, it’s pretty much on par with similar single-band receivers (which were still quite common in mobile phones at the time of Librem 5’s introduction) as long as you get almanac and ephemeris data up-to-date, which unlike on many other phones isn’t automatically pulled from the Internet here (but can be done manually).
What’s not great is non-GNSS location estimation, made even worse by recent MLS shutdown. You can reconfigure Geoclue to use Google for that, which will make it work pretty well, but then it will be using Google 