You've probably read some of my posts in this thread, and I've read it all too. I'm glad some people had luck, but I never had permanent luck until I got my phone replaced by Apple.
I've completely wiped my phone 2+ times through iTunes connected to a computer. Restored nothing except iCloud. Sometimes it worked good for a day or two, but the issue always came back. I have a Series 5 Apple Watch. I tried wiping my phone and not even pair my Apple Watch to it and the issue still came back.
For me, I would even notice my cellular data would drop while using GPS. It would start looking for service for 5-30 seconds then get a full signal.
In the end, I think its an issue between GPS and the ultra wideband antenna which is used for 5G and devices like the Apple Watch, AirPods, etc.
When I got my replacement iPhone, I set it up as new. I have my Apple Watch paired, manually reinstalled all of my apps, and everything has been working perfectly for 2 months.
Getting the replacement was a pain. I had a ticket open where I was sending logs to an Apple Engineer and did screen recordings of the issue. I sent it in for repair and they couldn't even find an issue. Finally the Apple Store helped me out and performed an exchange/replacement for me. At this point, I still think it is a hardware issue unfortunately.