YouTube ReVanced is a modified YouTube app including background play and adblocker. Follow these steps to install it on your Android device.
1. MicroG
MicroG is a free and open-source implementation of proprietary Google libraries that serves as a replacement for Google Play Services on Android.
If you already have an old version of microG installed, you should uninstall it first from Settings > Apps > microG > Uninstall.
Download the recent microG Settings (clicking here) and install it.
Open it and click on Google Account:
Click on Add Google Account and follow the steps to add your Google account filling your email and password.
2. YouTube ReVanced
If you already have an old version of YouTube ReVanced installed, you should uninstall it first from Settings > Apps > Revanced Extended > Uninstall.
Download the latest YouTube ReVanced (clicking here) and install it.
Now you should see a new YouTube ReVanced in your apps, open it and enjoy :-)
Note : if you want to open Youtube links by default with ReVanced, you can do it by going to Settings > Apps > YouTube ReVanced > Open by default > Add link > YouTube > Open supported links > and select all links.