Useful toolkit.
The application allows you to search, install and update software directly from the release page of this software in many sources. Why do you need it?
For example, you are using an open source application that for some reason is not available in F-Droid repositories. To update it, you need to find the release page of that application, for example, on GitHub, download and install the package.
This program will do it for you almost automatically. If the link to the release page is known - add it and use it. If it is not known - use keyword search, choose from the output, use it.
https://github.com/ImranR98/Obtainium
Are you trying to install an update from GitHub to F-Droid app? This will not work because F-Droid apps built with different signature. You should uninstall F-Droid app in order to install updates from GitHub or Play Store. Or you can add source from F-Droid to keep updating app from there.