While I’m not afflicted with syncthing much, it appears to me (probably too late), that this is a great opportunity for some students to work on the missing Go support for the Android Storage Access Framework.
@calmh: yes, that would create some paper work for you, if somebody is interested, but this is a real show stopper for syncthing.
That would be neat. There are many other good ideas as well:
I can say up front that unfortunately I do not have the time and energy to drive this home, paper work wise. However if someone else does that I would be happy to mentor and help students that take this on.