Setting Chrome mailto handler via Configuration profile

Based on what I'm seeing in the Google Documentation, it looks like any user can override this "recommended" setting. I suspect any registration of a mailto handler at the OS-level overrides this setting (setting the default mail program). Some tools like duti can set the default mailto handler for a user at the OS-level and may be closer to what you're looking for.

I tried that as well, that will let me select Chrome as the default mail client, which is fine, but it does not "start" a new email when clicking a mailto link

It seems like Google doesn't support this being set as a policy anymore, if they ever did. If you go to chrome://policy/ after applying the setting you'll see a 'not supported' warning for that preference.

Gmail is not an application. It's a web service you access through a web browser. The macOS Finder, which handles the associations between things like mailto links and mail apps like Apple's Mail or Microsoft Outlook, won't recognize Google Chrome (a browser) as "Gmail" (a web service).

Years ago, I believe Google or a third party provided an app that could act as a go-between to let you specify Gmail as your "mail app", but I think that project end-of-lifed.

Hmm strange, I see the "not supported" thing.
But according to the docs it should be possible, wonder how it's done.
https://cloud.google.com/docs/chrome-enterprise/policies/?policy=RegisteredProtocolHandlers

@henrik.schack I experimented with the policy example Google provided on that page but couldn't get Chrome to honor that setting.

However, I did find several "mailto" extensions for Chrome and this one seemed to work well:

https://chrome.google.com/webstore/detail/mailto-for-gmail/dgkkmcknielgdhebimdnfahpipajcpjn

You can use a Jamf manifest in a configuration profile to install this extension. I have instructions here.

Keep in mind this will only work when clicking mailto links in Google Chrome. But maybe that's good enough.