I came across iYTBP - injected YouTube Background Playback. It allows one to

1. view 2k 60 fps videos in app

2. background playback

3. download for forever

4. dark mode

5. no advertisement ever

6. VP9 codec

7. loop playback

8. pip mode

and much more without rooting your phone.

https://forum.xda-developers.com/android/apps-games/app-iytb...

This app is also available by Youtube Vanced name in XDA app store for free.

Alternatively, just make the public playlist of videos you like to watch and use youtube-dl cmd tool to download all those videos inside Android using Termux app. I prefer this method over the earlier one.