Hi, I’ve reviewed a bit of your project, congrats by the way.
If I understood correctly you are developing for embedded (AVR, STM32, RPi) but you use native to test, right?. I would have suggested testing directly to the platform, but as you need googletest that would be quite difficult to achieve.
Now, besides what @maxgerhardt said about cross-compiling I think another possibility would be to mix that idea with the pio-remote functionality and remote testing. At least by what the wiki says it should work.
That way, you cross-compile against only one platform Linux ARM and then you can pin-up the version of the compiler. Also pio remote would allow sharing hardware among your team, something that given the situation could help develop your project even faster.
By the way, pio-remote used to be limited for free users, but by what this announcement says, it looks like that changed.