The typical distro’s installer will just take care of setting up GRUB for you, don’t worry about that. I’m doing something similar with my home partition, except I made a home partition with all the expected user folders ~/Videos ~/Documents ~/Music ~/Games etc and then used overlayFS which keeps ~/.config/ and the like separate for each OS partition while letting me share everything else.
Apple by this time next year: We need to epoxy the entire airspace inside the new iphone because… waterproofing? Sure waterproofing I promise that’s why we did that.