Hi,
I can only tell from my test - a windows 10 could join a S4 domain easily and seems to have no problems at the moment. It was fast and the procedure was exactly as in Win 8.1 and 7. Windows 8.1 should have no problems as well. But you should really test such scenarios before going live.
Regards
Seems to work ok. Shows up in umc Computers: as Windows 10 Pro (Operating System) and 10.0 (10240) (Operating system version) in primary group Windows Hosts.
It all looks radically different in the Windows 10 interface, takes a while to find stuff. Shares seem to integrate ok, but can get lost in the complex layout on a busy power user’s explorer.