[Samba] Fileserver advice needed

[Peter Pollock]

I have a domain with two Samba DC's

I don't want to use either of them as a fileserver, so I want to build a
separate file server which is not a DC, which will deliver all the files to
the lovely little windows users (including their roaming profiles).

I've been looking online and there seems to be a thousand different ways to
"join" my fileserver to the domain, but most of the walk throughs are
outdated.

If I'm right, it needs to be a member server.... Right?

Can anyone point me to a walk through for such a thing (I'm using
Unbuntu 20.04).

It seems like it should be really simple.