If you are on the same OS then symlinks work so that DT thinks the location is the same. Not sure moving between OS with the different files systems…I do move between computers but I don’t bother with a library. I start DT with the Memory option so a temp virtual library for that session that gets erased and I just rely on the xmp files for what I need. Your situation might be what the local sync is in place to try to handle but again not sure about this between OS?? https://www.darktable.org/usermanual/en/local_copies.html