How to block youtube ads on ios using the youtube app and not a website?

It is a big pain to do so. Easiest would honestly to just do free trial every month. Google watches and knows it is you so it probably doesn't even matter if you make a new account

You could install pi-hole and a vpn service on a Pi and have your phone constantly on that vpn.

Use Android and download newpipe.

#nothelpful

Is YouTube Vanced a thing on iOS?

Easy:
1) start video
2) jump forward to about 5 seconds before the end.
3) watch the final seconds
4) click on replay icon
5) enjoy without adds

Pay for YouTube Premium, if available in your country.

@CoffeeAndHate im asking if there is a way without paying like on Android

You didn't mentioned that you don't want to pay money.
The only way I see to block ads on iOS without jailbreak would be a VPN based ad blocker. But reading articles on the internet, it seems that Apple might have banned all of them.
There is no other way without using an alternative YouTube app or tampering the original one.