A fix for the youtube login problem when you are logged in as the first login (/u/0/) with a google business account that does not allow youtube logins and you will always redirected to admin.google.com.
For example, you are logged in with multiple accounts on google and the second login is your account you want to use with youtube.
Copy the login link from youtube:
https://accounts.google.com/ServiceLogin?service=youtube&uilel=3&passive=true&continue=https%3A%2F%2Fwww.youtube.com%2Fsignin%3Faction_handle_signin%3Dtrue%26app%3Ddesktop%26hl%3Dde%26next%3D%252F%253Fgl%253DDE%2526tab%253Dk1&hl=de
This link tries to login with the first account.
To login to youtube with the second account, you have to attach a „&authuser=1“ to the link: