As a YouTube Premium subscriber who sees no ads, I find sponsor segments to be the real bane of my existence.

I simply don't use the YouTube app on mobile. I use YouTube via the brave browser which automatically blocks ads. Not the best experience since you can't background videos playing, but it works for me.

AdGuard and use the web version of YouTube.

You can't. And I literally switched to Android specifically because of this reason.

Now I use youtube vanced, and as a bonus it includes sponsorblock that saves me a ton of time while I watch videos. It also plays videos while phone is locked, useful during jogs and working out.

You need to jailbreak for that, and there are multiple adblocking tweaks. You can also add the iSponsorBlock tweak in the mix to skip paid video segments.

I think using an adblocker and uninstalling the YouTube app should be sufficient. The downside being that the playback quality is worse (720p max, I think).