I haven’t found a link to this forum on the tectonic website nor on the git hub repo. The only time I’ve seen this forum mentioned was when tectonic runs. I guess that’s something on the backlog.
Edit: Submitted a pull request for this on the git repo.
The next big piece of work I plan to do is to revamp the static website a bit and write a manual, both of which will link here much more prominently. Unfortunately I’ve been swamped lately.