Tried NextCloud with Talk module?

NextCloud allows you to share a folder but for upload only.

deleted by creator

Neither is their CEO.

Anecdotally, I am writing this comment from a 7-year-old Chromebook. Owing to software updates, it’s not as snappy as it used to be (therein lies the irony), but it’s still usable up to its Linux container. The battery is dead but I don’t want to get rid of it because the screen is still nice and bright and the hardware build is otherwise fine.

I just wish, though, I could boot proper Linux off of it and I could upgrade memory and storage.