instead of installing the youtube app, make a shortcut on your phone that opens youtube in a new tab on your browser
why? because there aren't ads!! (if your browser has adblocker, that is...)
HOWEVER there's one feature i like in the youtube app that i like that's missing from browser: tapping fullscreen automatically rotates the video, ignoring "portrait orientation lock". To make a video truly fullscreen in browser, you have to manually swipe down and unlock it, and then re-lock it after you're done.
My solution to this (and a bonus rec!!) is to set back tap to lock rotation (settings > accessibility > touch > back tap). Now you open a video, make it full screen, tap the back of your phone 3 times and woah it flips to fullscreen. No fumbling around with 'control center'. People are impressed. Tap 3 times again when you're done and it flips back to normal. swag