Not sure what you're on about, its right in F-Droid [1]. What is or isn't on iOS is in Apple's control. I recommend to take a look at Nextcloud. You can use it to control your own files, calendar, etc without some third party using it for data mining.
Only recently started playing with SyncThing (about the time SpiderOak's warrant canary expired).
To my mind, the Android app leaves a bit to be desired. Usually you don't want your phone to hold local copies of everything in the shared folder(s) as it is usually space constrained. You want to be able to view and pull files down as desired (possibly with the option to flag individual files to always be cached locally).
