Mods can be installed to your Documents/My Games folder and a Starfieldcustom.ini file created with 2 special settings. Then Starfield should find them even on the Game pass version. See the instructions for various mods. The exception I believe are mods that use SKSE but I believe there is a workaround for that too.
However, I read something about being able to change permissions on the install folder with some special terminal you can download, but I can't remember the name.. It was in one of the other Starfield posts from a few days ago (can't be more than two or three right..?)