Disable uploads for all users, including admin

Nextcloud version (eg, 10.0.2): 11.0.1
Operating system and version (eg, Ubuntu 16.04): Centos 7
Apache or nginx version (eg, Apache 2.4.25): apache 2.4.6
PHP version (eg, 5.6): 5.6

I am looking for a way to programmatically disable uploads and if possible file edits, but still allow file access and removal. The limit needs to include the admin user as well rather than being set by the admin so this would be done on the server itself rather than through the NextCloud interface.

The way to go is normally to allow users only to use storage shared by other users (giving them a quota of 0), and if you share you only give read access. Problem for a admin-user is that he can change his quota, this would only help if the system quota of the data-directory is exhausted.
Files and folders could be used from external storage and in this external storage you can try to solve the task to allow only deletions (but not uploads or changes). Not sure if Linux ACLs on the fiile system can do this job.