[feature request] mark apps as upgradable that can't be updated automatically

**Is your feature request related to a problem? Please describe.**
I'm not getting informed of app updates that can't be updated automatically. I only recognize it by comparing the installed version and the latest available version manually.

**Describe the solution you'd like**
A simple message would suffice, like:

> The new version of $appname can't be installed automatically, please uninstall it and install the current version manually.

Additionally, show it on the Updates tab.

**Describe alternatives you've considered**
A notification would also be nice, but might be overkill.

**Additional context**
Here the author of the app changed the signing key, resulting in me having to uninstall and reinstall the app manually. Version 2.4.10 was installed, while version .11 and .12 were available, but no update was suggested.