Has a private instance of GitLab (or similar) been
promote contribution by online visibility and easier collaboration
(discussions in issues, pull requests, etc, similar GitHub).
I find email to be inefficient.
Email is a very deliberate choice. I find it to be much more efficient.
But, if you prefer web-based tools, we have those! You can interact
with the mailing list on the web at
just like it was a web forum,
and you can browse the Git repositories at https://spectrum-os.org/git/