> Has a private instance of GitLab (or similar) been considered, to
> 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
https://spectrum-os.org/lists/hyperkitty/ just like it was a web forum,
and you can browse the Git repositories at https://spectrum-os.org/git/.