Installed tab: Distinguish between the same app installed from multiple sources
When an app is installed from multiple sources, it looks weird and is a bit confusing to have two duplicate entries on the Installed page. When there are two apps with the same id installed, either they should be grouped together, or each row should show its source.
The first Text Editor entry in the screenshot above is the nightly version, so a separate entry for it is ok. The other two are, respectively, the Flathub and rpm versions.