Hello.
Thank you for your interest.
This package lets you set up 2FA on a peruser basis.
So it's either enabled and available to everybody or disabled and not available.

But not everybody must use it. Users can choose not to enable it on their account.

Did you mean you want it to not be available at all for certain user groups?

If that's the case you could achieve this by using concrete cms permission.

The package offers a block to add to any page that lets users set up 2fa on their account. Using permissions you could make the block only available to specific groups.

Please let me know if anything is not clear.