Thanks for these words, I appreciate it a lot. For some things I guess it's better not to look at how it's done in DarkRadiant and to keep an open mind for better architecture , but overall it has come a long way since we forked GtkRadiant.
As far as development is concerned, I guess you're already doing a good job, so just keep it up. As usual in open-source development, the most useful fork will gain popularity, so I think we don't need to keep merging back into my upstream repo. But it might be useful to sync up with OrbWeaver's fork over at gitlab.com from time to time, and vice versa.
As far as releases are concerned, in the past I just picked a suitable time between a couple of fixes and new features to call it a new release. I have some scripts and installers helping me do the thing on my local machine (but this is all Windows based and probably not of any use for you).
There's also the darkradiant.net domain which could go into better hands, I'm still holding the domain account for that.
(And before I forget, I've picked up from the wxWidgets release notes that there might be some sort of dark mode implemented for the Windows port, I know some around here might be quite happy about that.)