I am on the X Compact at the moment, but the GPS problem seems to be an universal LineageOS problem. For us, GPS stopped working in mid-July, too. Same problem, lots of satillites in view, but none gets locked. In the GitLab of LineageOS there are many issues of different phone users experiencing the same problem on LineageOS 16 and LineageOS 17.
Thanks for the answer.
So my tests are "localization with GPS only". Outdoor a TTF is made but after few minutes, and then without disconnection. So it is working, but not as fast as it should do at first. Strange.