Hi,
I think this is mainly because the questions are not really defined so
I made a little sketch here: (anonymous) | Sketchboard
For me (that on NixOS I’m a still non-contributing newbie) git repos +
ml are the BEST option because an ml can be hosted by anyone and change
hoster does not change nothing more than few URLs and git is a FOSS
software anyone can grab and use, also well integrate di both Vim and
Emacs (witch already have very good MUAs integrable in a snap with
git&other SCM) and many other editors and IDEs. Also using such
solutions force users to know FOSS software instead of using and know
proprietary or semi-proprietary platforms.
It scale well since not-exactly-small project like Linux kernel use it
since many years.
– Ingmar