How do you unenroll a console from a account that didnt enroll it?

If you're enrolled in the Minecraft beta you need to unenroll from the same (you can unenroll from the Xbox insider app)

You can remove your console from the program by the Xbox One console with the Xbox Insider Hub installed. To stop participating in the program on that console, launch the Xbox Insider Hub app and go to Settings > Manage Devices. From there,
you can unenroll any console registered to you.

Note Unenrollment can take up to 72 hours to complete, during which time you may still receive console, game, or app updates. When the unenrollment process is complete, your console may be reset to factory defaults. If resetting your console to factory
defaults is required, your data will not be erased.

https://support.xbox.com/en-US/xbox-one/console/xbox-insider-program

This isn't an option for me as I bought the console used and the previous owner enrolled but I do not have access to their profile to unenroll and it doesn't show my console as enrolled under my gamertag. However it is certainly enrolled.

Are you in an Insider preview ring?

OSU's cannot be used on a console enrolled in Insiders.

The console must be unenrolled from Insiders prior to attempting an offline system update (OSU).

Did you do a soft reset ?

If you bought a used console you can only unenroll from the profile that enrolled

You can however use the insiders app from a windows 10 machine with the said profile

But you can also do a hard factory reset

"I want to revert back to the normal homepage. When I hit view button on homepage, it doesn’t do anything."

As far as I'm aware the New Experience Dashboard is only available to select consoles enrolled in a Xbox Insider preview OS. You would have to unenroll the console from the preview. Use the Insider Hub to unenroll. The General Available OS will be installed once you leave the preview.