It’s actually “easier” to sustain a FOSS app on Apple for this reason
You put a price tag to the client/app and there it is a business model without relying on donation, because the user cannot sideload without being a dev :)
The Way Home. It's a pixel-art roguelite made in Godot. It's not open source, but the author did a hell of a good job making it 1-hand playable, and pretty fun to boot.