the replacement kits are mechanism of Qt Creator to re-create older kits that are no longer installed but still used by projects, to be able to keep building those. You can ignore them, to my experience, QtC is a little inconsistent here. For the new installation, you will need a proper new kit, not such a replacement one.
In general, after installing Felgo 4, you need to set up your Android toolchain (it is recommended to use wizard in Qt Creator for this, in Preferences -> Devices -> Android). You can also find the guide and recommended versions in our docs: https://felgo.com/doc/felgo-deployment-android/
Then you need to add the Felgo Android package via the maintenance tool.
After that, you should have a proper Android kit set up to select and build in Qt Creator.