I write code.
Agreed, we should stew on it for a bit. Will be valuable to develop out the templating stuff regardless, let's just pick some arbitrary temporary way of selecting the theme for now.
Though that's not exactly zero-config, I guess.
Could be solved with a whitelist of hosts which are allowed to customize the UI.
Note: because themes will likely often be dependent on the set of installed extensions, it would make little sense to fetch them from an arbitrary URL.
Hm, I didn't see the themes as something arbitrary which would be fetched remotely. I saw this more as a selection between themes installed by the sysadmin.
I personally haven't used webmail as my daily driver for a long time, so I can't say. I designed the sr.ht style so that it would be unopinionated and easy to get functional UIs out of, so my web UIs basically write themselves at this point.
I'm not a huge fan of that style (even when it was the modern gmail look & feel), but since a main feature of this project is user customizable templates, I'm not especially concerned about what the defaults are.
That would be helpful. We should also use this tool to verify our implementation: