Edit: I added the repository and it says the microg stuff is already installed: microg.org/download.html
Edit2: as @scottmeme said here, I had to download the YouTube apk.
Edit3: I can patch the downloaded apk, but still working on installing it.
Edit4: Getting the error “App not installed as package conflicts with an existing package.”
Edit5: I think I’m going to have to get ADB going on my computer in order to uninstall the original YouTube from my phone.