arkTube is an ad-free and easy-to-use YouTube video downloader for Android that use YouTube-dl command line program to its full force.

The Android app is extremely lightweight. Unlike other YouTube video downloaders here, this one does not have a dedicated YouTube section. Once arkTube is installed on Android, you can download videos right through the official YouTube app.

On the Android app, you will find options to set a default video resolution, choose an audio codec, download in MKV format, and more. However, some of these features are restricted and can only be unlocked once you buy the developer's donation package--arter97 Donation Package

How to download YouTube videos on Android using arkTube
Install the app and give permission to access media.
Go to YouTube and select the video that you want to download
Tap on the Share button
Tap on the icon that is labeled Video
Select the resolution
Wait for the download to complete.