Nowadays you can use uBlock Origin on iOS devices - the Orion browser by Kagi (the privacy-focused search company) supports web extensions. I’m using it along with SponsorBlock for a totally ad-free YouTube experience. No affiliation, there have been other ad-blocking apps on the App Store for years, but imo this one is the least sketchy - and free to use.
Also side loading and alt app stores should come to iOS (at least in the EU) soon so keep an eye out for NewPipe iOS edition!