There’s now a fully open source ios app in beta: https://forum.syncthing.net/t/beta-test-my-new-ios-app-for-syncthing/22457

I am not the creator, funnily that is/was one of the Lemmy creators: Nutomic :)
I am a syncthing co-maintainer that kept the android app on life support since a while.

Oh don’t worry to much, mine too: If there wasn’t an alternative for syncthing on android, I might have kept it on lifesupport :)