I had exactly the same problem -- not everyone had the same mapped drives as me, or mapped to the same letters.
After much searching J'ai trouvé a context menu extension named Path Copy Copy on GitHub (https://pathcopycopy.github.io/) which is an extended version of a similar, older extension (called Pathcopy) has quite a few options for copying paths as text, including one for UNC paths -- example of the options available are shown below:
Vous pouvez aussi choose to show only one or two lines on the base context menu, par exemple vous pouvez have two lines, Copy Long Path, and Copy Long UNC Path. It's great for emailing users in your company who have access to a network path, and if they have the same network mapping as you, vous pouvez choose the former, otherwise vous pouvez utiliser the latter.
Mise à jour : As of version 12.0, a new "portable" installer is available on the above site, which installs only for the current user into the AppData\Local folder. I've not tried this, but it could be solution for those who are prohibited from installing normally.