Turns out it takes forever again after rebooting the phone or restarting GPS apps. The cellular or WiFi positioning seems to be broken, and finding satellites takes a long time too. Once connected to a satellite, it lost the connection multiple times and jumped around on the map. So, it is very unreliable.
This is how the GPS worked on the Jolla C2:
And here the same route using S24U:
I put this in my feedback post. Feedback on Jolla C2 - #939 by lightstar