Wonderful write up, as always from Bartosz!

Here are some fun GPS projects I've found in the past, maybe others can add to this list.

GPS/Galileo/Beidou/Glonass status and error monitoring, open-source community-ran project: https://galmon.eu/

DIY GPS receiver using minimal signal frontend, FPGA Forth CPU for real-time processing and RPi running position solvers: http://www.aholme.co.uk/GPS/Main.htm