@Cilliers Denis - Automation Solutions-MR when you want to change deployment type from container app, you will also need to clear/update the linuxFxVersion property under siteConfig. This property is pointing to the image/tag which tells the portal it's a container app.
az webapp update --name appname --resource-group rg --set --% siteConfig.linuxFxVersion=DOTNETCORE|7.0
Also, make sure you use set, instead of add to update existing siteConfig
properties.