It seems quite incredible but this little trick WORKS:
- Log out of both Gmail and YouTube.
- Open a browser tab with the Gmail login page.
- Open a browser tab with the YouTube login page.
- Fill in your user credentials in each login page, but DO NOT log in
yet. Make sure the text cursor is in the password field on both
- Switch to the YouTube login page and press Enter to log in.
- Quickly switch to the Gmail login page and press Enter to log in.
Note: Experiment which first to login, Google or Youtube. The correct order changes.
[ All credit goes to Brother Lobster from a Google forum thread ]
I've tried it in Vivaldi and Firefox, stable situation of being logged in, with one Google account on YouTube and another on Google, for a few weeks now; does NOT seem to work in Chrome.