The type or namespace name 'UnityEngine' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'UnityEngine' could not be found (are you missing a using directive or an assembly reference?)

Process completed with exit code 1.

For projects targeting .NET 8.0 and higher, specifying a RuntimeIdentifier will no longer produce a self contained app by default. To continue building self-contained apps, set the SelfContained property to true or use the --self-contained argument.