[wltr]

Have you considered syncthing? There’s shiny new and super cool Sushi Train (or Sync Train by other name) app for iOS (I wish the author would make it a paid app, so much I like it!): https://github.com/pixelspark/sushitrain

Not affiliated, but a very happy user.

I mention iOS, because that was what I needed personally, as there was syncthing for Android since forever.