You may not find this answer satisfactory, but you could use Invidious from any browser. I have no idea if there are any Invidious-based iOS apps.
Youtube
Invidious certainly is a fine solution for casual watching. This might actually end up being sufficient in the long run as YT dives deeper into enshittification.
I used Orion for a bit too whatever Apple did to break it is annoying but I’ve moved back to Piped and while it’s not perfect I haven’t seen a single ad and I got sponsor block built in.
Some instances don’t work due to google cracking down but there’s plenty they haven’t got yet
I use fire fox focus browser on my iphone and that works great for blocking adds. Can only have one tab open at a time, and often times buttons on web pages just have a default icon.
I use Firefox Focus all the time for clicking various unfamiliar links on Lemmy and elsewhere, and it’s really good at blocking all sorts of online annoyances. However, YT ads are beyond the scope of what it can actually accomplish. Also, it won’t do full screen video.
It does full screen video and blocks ads for me.
I can even get it to pop out the video in Picture in Picture. All on the YouTube page.
Really? That is unexpected. How can there be such vast differences even though we're talking about the same app?