Hi,
A message to say that I still maintain/develop a little Devhelp, the API browser. (Since there is a devhelp tag here on Discourse, I might as well use it).
On gitlab.gnome.org Devhelp has been archived: Archive / devhelp · GitLab
The version that I maintain is here: GitHub - gdev-technology/devhelp · GitHub
I use it on a daily basis. I’ve released the version 50.0 recently. It is mostly for my needs, but it might be useful to other developers.
Note that the upstream/archived Devhelp and the Devhelp version that I maintain have diverged. The latest version in common is the 40.alpha. The upstream/archived Devhelp was modified to better support gi-docgen among other changes, which is not included in the version that I maintain. (For my needs I only use GTK-Doc). Note that in the past I’ve been an upstream Devhelp maintainer, and I’ve basically refactored almost all the codebase. It is still based on GTK 3.
Newer alternatives:
So there are plenty of choices 
Cheers,
Sébastien