Accounts can still be unlinked, YouTube just made it a harder process now (which was fucking stupid on their part).
https://support.google.com/youtube/contact/linkissue
Credit: HF
https://support.google.com/youtube/contact/linkissue
- Fill out all of the basic information on the page. Full name, YouTube username, contact email address (to make the process easier, use the email connected to the channel, otherwise they message the contact email saying they've contacted the email associated with your YouTube channel and any other backup recovery emails associated with the email connected to your YouTube channel.), email associated with your YouTube, country, URL, and everything else.
- Once you've filled everything out correctly, go down to the "Please select the issue you're experiencing *" and hit "Other".
- In the issue description box, fill it out with something such as, "Hello! I'd like to unlink my YouTube from the current email address to change it to one of my other emails. Can you please help me out with this? Thanks!"
- Check your inbox, support representatives usually reply within 24 hours. They will ask if you'd like to continue with the process. From here, they will email you back (probably in another 24 hours, which is their usual email response time) with a temporary account password. You will have to sign in at: https://accounts.google.com/ServiceLogin?uilel=3&hl=en&service=youtube with your YouTube username. Not an email -- and the temporary password they've given you. Again, this takes time, but you can at least change the email address now and fully secure your channel.
Credit: HF