Open core legacy patcher has kept my 2012 MBP able to run modern versions of macos (currently on latest update to Monterey). No stability issues, but AirDrop is flakey and I am no longer able to run anything in a VM using Apple’s hypervisor. It runs well; might be worth looking into for your use case.
The Google Ara was supposed to be exactly this. I think it has since been abandoned. https://en.m.wikipedia.org/wiki/Project_Ara#:~:text=Google%20planned%20to%20launch%20a,planned%20consumer%20launch%20in%202017.