Installation process:
1. Install microG (if some other one is installed (not from this post), then you need to remove it and install this one)
2. Install YouTube with the add-on you need. topic.

I can't log in to my account via microG:
On some devices (especially older ones) there is such a glitch.
1) It is necessary that microG be installed before YouTube, and not after. If YouTube was installed first, then just uninstall it and reinstall it. You may need to restart your device.
2) O