android options:
moz-extension://1a5a64a8-da54-4b41-8b1a-a6781fa54e13/options.html

desktop options:
moz-extension://9b21ad35-a3fe-4966-aef2-216d78c1c069/options.html

Works well, thanks.
What I would need is to have some fixed "favorite" fake locations.

Works perfectly though it's not pinnable to the toolbar (FIX THIS!!!),. so getting through the multiple layers of settings to actually change things is a bitch. Go to manage extensions, then options then "use fixed location" to nail a location down.

Thanks to the author.

Th extension does what it says, use the 'Fixed Location' option if high precision location is not important for you. Read the FAQ. It does not change IP Location though, only Broswer Gelocation is changed (even without using GPS).

Despite claiming to be configurable on a per-site basis, I was unable to determine how to do this (extensive searching). And, if the extension's icon is supposed to be visible, it is not on my system (FF 121.0), and while I can find it in the overflow "Extensions" button on the toolbar, it is greyed-out and unresponsive. I uninstalled it after an hour, as I need its capabilities for ONE site, not all sites, and it does not appear to have this capability.

The extension is working perfectly what I wanted.

Pros:
- does what it is supposed to do
- simple
- tiny, not bloated
- uses OSM/Leaflet for settings instead Google Maps, so additional + for privacy

Cons:
- lack of per site settings (my reason of 4 instead 5 stars)
- doesn't give button to turn on/off extension (the only way is via Fx built-in mechanisms)