Still supported, or not
It's could be a bind if you run say RHEL/CentOS 6 which is still supported by RHEL to which you may be locked for support contracts etc.
Until quite recently there were no Samba 4 packages available for it, apart from Sernet who then pulled their open source packages behind a paywall some time ago.
RHEL slipped out some S4 packages a while back but they are only at 4.2.x and W10 I believe really wants 4.3.x + for SMB 3.1+
Messy. Probably even worse if you run a NAS and rely on upstream firmware.
If I had my cynics hat on I'd almost say 'contrived'
But that would be too cynical, wouldn't it?