At least the message was observed before.
Does it help if you explicitly set the default launcher again in Settings - Apps - Default Apps - Home App?
If you are using the default Bliss launcher which comes with /e/OS, you could try whether clearing cache and storage of Trebuchet and/or BlissLauncher helps in Settings - Apps - See all … Apps - (three dot menu top right) - Show system - Trebuchet / BlissLauncher - Storage and cache - Clear cache (try this first) / Clear storage (this should reset the home screen and settings).
If nothing else helps …