Clicking on a file:// link does not work for local folders. On Desktop, it doesn't do anything. On Firefox, it opens a blank page.

Apparently, this is intentional as explained by @yuya-oc because:
- Accepting local resources would allow to execute programs via malicious link
- There is no situation where an user would want to share their local files without attached files.

In my usecase, we use Nextcloud to sync files within our group. And we have the same letter and path for local files. This is why we often share the file path instead of the file itself, to save data. We would love to be able to open the link directly.

It is reported on Github: https://github.com/mattermost/mattermost-server/issues/12042