Comment 22 for bug 1928434

That's because _test_and_fail_on_apple in DistUpgradeQuirks.py (see line 377) in the upgrader itself, is set to fail if vendor.startswith('Apple Inc.') OR if vendor is unknown i.e. /sys/class/dmi/id/sys_vendor is null (for example as it will be in WSL or just about any other system where DMI isn't implemented). Put a return after that and you should be able to force it (on your own risk).