Since the whole stack runs on your server there is no real way to ban anyone as such. Worst case is that you would loose access to updates, however all our app

Since the whole stack runs on your server there is no real way to ban anyone as such. Worst case is that you would loose access to updates, however all our app packages are MIT licensed (eg. https://git.cloudron.io/cloudron/nextcloud-app https://git.cloudron.io/cloudron/nextcloud-app ) as such you could just build the app image with docker locally and push to your server manually.