External protocol handlers may open URLs in new tabs. It's not clear if Sec-Fetch-Site: none is the right choice here. It seems to be the only choice since no origin information is available but an external application may have triggered the navigation without any user intent. Especially on mobile where it's sometimes possible to use a handler for an external app in such a way that it opens the browser again it might even come from web content.
External protocol handlers may open URLs in new tabs. It's not clear if
Sec-Fetch-Site: noneis the right choice here. It seems to be the only choice since no origin information is available but an external application may have triggered the navigation without any user intent. Especially on mobile where it's sometimes possible to use a handler for an external app in such a way that it opens the browser again it might even come from web content.