Hi,
on my Fairphone 5 with iodeo 6,2, at the installation microG was disabled already.
But after installing Shelter app to use a work profile, in this work profile microG needed to be disabled a second time manually by setting to “frozen”.
I have not tested disabling microG at first boot like you did but I suspect it only disables it not uninstalls it. You can go to Settings > Apps > Preinstalled Apps > microG Services and there completely uninstall the apps. Not certain if that will remove them from the Work profile, if not use shelter to delete them from there.
You will then only have GPS for location which will be less accurate, more battery intensive, and and slower than with microG but should still function correctly.
Sorry don’t know how to fully uninstall then, but can you check “System Settings > Apps > See all xyz apps” and find the microG entries for Personal and Work and at least disable them there? Check the 3 dots > Show System as well to make sure all microG bits are not enabled.
The microG Services app (the second app in the list) had the full range of “ugly” permissions, which a person with privacy intention don’t want.
This three microG app’s can be disabled, not uninstalled.