In my case with a Xperia 10 II, the GPS was able to see about 25 satellites but not able to use anyone. This is because I received Android 12 pre-installed while Android 11 is required even if the Sailfish OS installation guide does not warn about it.
To fix the problem, I had to install Android 11 using Emma the flashing tool from Sony
After, the installation of Sailfish did not present the GPS issue. I hope this helps.