iOS has terrible choices when it comes to privacy and/or Open source. Apps that put control into the users hands are in direct conflict with Apple, and many times from what I know certain software licenses have issues getting approved there. See if Raivo is still around (may be spelled wrong).

Check out Techlore as well for recommendations across the board, before he went to a Pixel he ran an iPhone for a while and had a decent list of stuff for them IIRC.