If two different accounts enroll the same console, do both accounts need to un-enroll it?

you'll need to do it on the Xbox Insiders app on the console. go to the game > manage > un-enroll

Also uninstall the version of Minecraft completely off the console.

The app will be in the ready to install section and you'll need to enroll it again which takes time. You will however need to un-enroll your current console if you're going to sell it.

You'll be able to find more information on what to do on the preview forums

forums.xbox.com/.../default.aspx

I had the same issue myself, had a few different consoles due to disc drive issues, put the preview dashboard app in your pins, when you sign in on another console your pins come with you, load up the app un-enrol the old system and enrol the new one, i
think this can be done three times. There is likely another way but this worked for me

Hey mauretto63! I can confirm you are in the preview program. If you'd like to un-enroll you will need to download the
Xbox preview dashboard app. If you have any trouble un-enrolling you will need to post in the
Preview Program Registration Support forum. Thanks!

It is enrolled in the insider program on both accounts, yes only fortnite we know this cause we play minecraft and the sims 4 also on this same console without any issues. Thankyou for responding