I asked openwrt discourse administrator, and just checked it myself on the fresh locally installed discourse 2.5.0.beta2:
It seems that dark theme has been disabled, as F-Droid runs the same version (2.5.0.beta2). Just go to the https://forum.f-droid.org/admin/customize/themes and enable it for users:
If there is only Light theme in the list:
you should press Install → Create new Fill the name, “Dark” for example with type Theme:
and then, on the next step, assign the Dark color palette and make it available for users:
Dear administrator, is any update there? Can I help somehow?
I tried to do this. But none of this is there:
At first I only have this:
When creating a new theme I only have light color pallete for selection:
Try to enter Colors tab (to the right of Themes tab) and add dark color palette and make it accessible for users.
I think I added the theme. I have no idea where I’d select it as a user though. Also the F-Droid header text is black on black now in the preview 
.
Edit: I found where it can be selected. The selection box didn’t show up immeaditely.
In terms of fixing the black-on-dark, there’s been talk and collaboration on the forums of updating the forum icon in anticipation of a new F-Droid Forum app and creating a bespoke icon/header for the forums.
If people here are interested in the latest work (see link below) tell me and I’ll push it to the existing Merge Request, or make a specific MR for just this:
Marcus, thank you! 
The easiest way to fix the F-Droid header is to add an outline. Not sure if Discourse can server two different versions for white and dark color schemes. If you point me to the header’s source (svg?) I could try to add an outline.
The svg is in the fdroid/artwork repo.
Yes, and if people are interested in an outline version of the “forum” artwork that we’ve been experimenting with, see below. EDIT: I’ll admit that the word “forum” below is looking a bit crusty with the outline so I’d be open to removing that word. I’ll leave it to others to decide what they want to do.:
Discourse is also mailing list and long-form chat room in addition to discussion forum so the the word “forum” is really crusty.
What about inversed version, same as OpenWrt does:
Thanks for the info.
How about this?:
I did try inverting it but I didn’t think that it looked good. Maybe because it’s a slab-serif font. The white outline seems to match the white outline in the blueprint-style icon.
EDIT: If people like the above then I’ll do a new Merge Request.
Considering a forum is just a public gathering place for discussion, I can think of no better word.
That’s fair.
How about this? I tried to integrate “forum” without it looking crusty or making the image too wide for phones (click to enlarge).
EDITED 1 hr after first upload:
I can think of no better word.
It’s no matter how you’ll call it. This word is superfluous.
I hope you don’t think it’s worth adding website here:
Do you?
This forum sign looks very strange and absolutely unreadable, sorry 
How about this?:
The word F-Droid without next ‘forum’ looks fine.
But the shaped background is excessive here (leave it for phone icons)
I’m for this variant:
I’m not against the new icon, colors and adaptive style looks fine. The only thing it’s why copyleft external circle touches the top and the bottom lines. Moreover it’s very bold:
I’d say it’s not superfluous to the unacquainted visitor. Would we want a potential new user to be confused as to why the supposed F-Droid website just looks like some forum where people discuss apps or something?
By making it clear that the user is only on the F-Droid Forum they are able to infer that this is not the official F-Droid website.
If the user is already somewhat aquainted with the F-Droid icon, the blueprint-style icon might also help imply this site is a “formative part” of F-Droid’s experience, so to speak.
For myself, I find switching between the F-Droid Forum and Official website tabs in the browser can be quite confusing at times so I’m actually looking forward to a different (fav)icon for the two sites.
Please click the designs to enlarge them to 100% scale. Having said that I’ve made the bubble larger now (see below). EDIT: If I were to make it any larger, I’d do improved outlines for the bespoke typography.
I removed the background grid in the above version, but yes I can see why one might prefer the version without the squircle in the header location (see below)
All fine points. I only did make the symbol larger and bolder for favicons initially and I started reusing that method for the “forum icon” variant but in hindsight I agree with your critique.
UPDATED BELOW (favicons unchanged) (EDITED 20 mins later: “forum” typography slightly improved + spaced better from 'F-Droid"):
unacquainted visitor
it’s already present in the address bar:
Let’s Encrypt isn’t worries to get confused:
OpenWrt isn’t worries to get confused:
Even discourse isn’t worries to get confused:
