The app in the screenshot is URLCheck, it is my “default browser” and allows me to see where a link is going and edit it or choose what to open it in.

It’s showing that the ! link I tapped on the bottom of the screen got an “https:/” (one slash) put in front of it instead of being treated as a proper link to a community.

The same thing happens with @ links:

A screenshot showing that a user-link from a post summary ended up with part of a protocol prepended to it