I just tried AdGuard with safari and got YouTube ads. Do you have to configure something special?
I will check what particular settings I have for AdGuard when I get back home this evening. I don't recall anything particularly hairy but it has been a few years.
There‘s a checkbox called “Enhanced Protection” (name might vary, I have the app in another language) that specifically says it’s for stuff like YouTube
do you use the AdGuard app or just the DNS?
Safari with the uBlock Origin Lite extension works well for me - even with "Web page Contents and Browsing History" permission set to 'Deny' for all websites.
With Safari and the very first free-to-use extension I picked years ago (AdGuard, IIRC), I don't see any YouTube ads on iOS.