Much if not all of the changes required for python3 compatibility have already been made to both osmocom and boatbod repos. Max has patches for his branch to address gnuradio 3.8 API changes, but these are an add-on that has to be applied if you want to run that version. Personally I've not tried a gr3.8 build yet since it is still not the mainstream default and I don't have a spare development machine to set up that way.