plenty of Firefox forks are still thriving and getting updates

is it possible he forgot to select pro in the install menu a pro license will activate home no problem

should work just fine just look at the wiki for os-prober to get it in your grub menu

if your using grub you just need to install os-prober and re build your grub config and then you can boot windows from grub even on multiple drives

or host your own with nextcloud or casaos or the like