I picked up a GLiNet C3000 cellular modem that has a built in GPS antenna and can run GPSD (as it runs OpenWRT), found this old addon and got it updated to work with later versions of HA.
Your post was great and I finally got it working after resolving a number of issues with “other” stuff. HACS wouldn’t let me install the repo and so had to install manually. Also the GLiNet AX3000 wasn’t producing GPS data until I corrected the antenna setup.
Others might find it useful to know that you can run “gpsmon” on your router to validat e that the data is being produced correctly. If its not updating with lots of data, you have got somrthing wrong. My issue was that i’m using a Pepwave 40G and had connected the antenna labeled GPS to the GNSS port on the router when I should have connected the 4th mimo cable and not used the GPS cable at all.
Also I got configuration errors from HA with the template config and updated “float” to “float(0)” to provide it with a default: