Completely disable client sync for external storage on the Nextcloud server

We would like to use some external SMB shares as additional, external storage in Nextcloud.
Those SMB shares are being used internally, they are not directly accessible from outside our networks.

Sometimes a user or group would like to share a folder on those SMB file shares to an external party the easy way, this is where Nextcloud would come into play.

This works fine with Nextcloud, however, there is one problem.

If an SMB share is connected as external storage and assigned to group, let's say 'Project Manhattan', all users of this group get a desktop notification from their Nextcloud desktop clients that there is something new to sync and if they would like to do that.

Some user of Project Manhattan will notice that this is their huge SMB filer share and they don't need to sync this. But others won't, will click yes and terabytes of data will beginn to flow.

A little bit later the operating system of these peoples computer will start complaining about a full harddisk. As they are engineers they fix things themselves, so they launch treesize or something similar and will then remove this huge 'Project Manhattan' folder. What was it doing there anyway? Now another user, working on the SMB filer, begins to wonder where all the calculations have gone.

It happened like this with our test group. Except they do not build bombs, of course.

We are using Nextcloud (previously ownCloud) since a long time.
I saw this feature request more than once over the years, but none of them seems to be open since quite some time. Please indulge me for asking again. :)

I'd appreciate an option on the server to completely disable the client sync for external storage. Global or per external storage does not matter.

No files, tests, or entry points are named in the issue. Start by locating the server handling for external storage and desktop-client sync prompts, then determine how a global or per-storage setting could prevent synchronization while preserving external sharing; done means the selected external storage no longer triggers client sync.