Ok, I literally just figured this out after posting my question. Figures.
See below:
1. Navigate to your site's /admin or /edit page:
2. Select 'Groups Manager'
3. Select 'Content Library'
4. Look all the way to the right, for the 3 dots/ellipses , click them:
5. Click 'Configure DCAT'
6. Toggle between 'Groups' and 'DCAT Feed' depending on your requirements, but here is the 'Groups' selection, as expected previously:
It looks like Esri is planning some changes to this section, as evident by this alert box:
Hope this helps someone else.
Regards
dcat configure-dcat missing-dcat-arcgis-hub missing-groups-manager