Disabling Gutenberg Duotone Filter?

We maintain multiple websites for a university, and have mostly been able to disable the features of Gutenberg we don’t need so that end users have a fairly simple interface for editing without going outside of the branding guidelines too much.

But I’m struggling to find where to disable duotone (introduced in WP 5.8) and can’t find any related documentation. Can anyone point me in the right direction?

Thanks!