I had the same error as you but i managed to fix it. Your error is coming from module rules named ‘RD’ which stands for Rider. You are getting that error because you chose to install RiderLink plugin in Engine instead of Game.
Your second problem should also be fixed because you won’t be getting any errors. I have managed to upgrade blueprint only UE4 project to UE5 and then add C++ classes with no issue. The only issue that persists is that there are some false positive errors in Rider so i have to compile my code through UE instead of Rider.
As stated in this blog about Rider for UE5:
There are still a few known issues with Unreal Engine 5:
- Unreal Engine 5 bundles an old version of the RiderSourceCodeAccess plugin that doesn’t have support for macOS. In order to be able to select Rider for Unreal Engine as your IDE of choice on that platform, you’ll need to download the latest version from the trunk here and place it in
{GameFolder}/Plugins/Developer/RiderSourceCodeAccess. - The RiderLink plugin doesn’t work if placed into the Engine. It should be placed into the Game only. Learn more about this plugin in our web help.
- There are some false positive errors in .build.cs files when opening .uproject on macOS, which we plan to address later.
I hope this helps you!