What you want is either an alternate location services provider that can generate plausibly fake location streams or a middle layer that is deeply embedded in the OS. Privacy/security-focused Android projects use one of these techniques, but usually with real location data. For example, using LineageOS with privileged microG comes with alternative location providers like Mozilla's.

My personal knowledge of the actual fake data generators is pretty bad, though. I haven't personally spoofed location in a way that's intended to work in the way you need.

For the microG version, you'd be using https://github.com/microg/UnifiedNlp with a spoof plugin. I'm not aware of a spoof plugin but wouldn't be surprised if one existed. There is also this app but it looks pretty crude: https://github.com/wesaphzt/privatelocation

IMO to defeat spoofing detection you'd need something a little more sophisticated. Something that embeds a proper simulation of a person traveling, then being still, and having some biased noise / systematic accuracy reporting added depending on the location. Could be a good side project for a lefty to work on...