One of the TODOS for T251182 is to document in the GSoC/Outreachy mentors' guides venues to recommend to students for hosting code repositories.
It looks like there are a few resources on MediaWiki.org related to this topic:
https://www.mediawiki.org/wiki/Git/Creating_new_repositories (for administrators)
But, there isn't a resource that lists all the venues in one place and recommend when to use what. Like when to use:
(Might be more venues that I am not aware of Gitlab, SourceForge, etc)
This resource might be helpful not just for outreach program candidates or newcomers but probably for the broader Wikimedia technical community, especially for folks who are into developing tools, bots, etc.