Hi @jamesc welcome to the /e/ forum. Do you already have one of your “alternative” launchers set as the default launcher?
If yes, and you plan to stick with the alternative, please can you try to delete cache and delete app data for both Bliss and Trebuchet. (Trebuchet is already installed as a system app, so in Settings > Apps and notifications you will have to use “show system” in the top right 3 dot menu to find it.)