We are also thinking about F-Droid support (either through an official F-Droid app, or through a custom repository offering apps both with and without Play Services).
However, it will still take a while to evaluate all options. Thanks for your patience! ^db
Threema in F-Droid would be indeed great. If the server part then could be open source, too, i would be totally happy.
@threemaapp Be welcome approaching us! I'm one of the F-Droid maintainers, and I also run my own repo – plus I'm using Threema myself (multiple licenses for multiple devices). So should there be questions, we're glad to help you with those steps.
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!