LWRP 5.8.2 compile errors

Need help in debugging an older AR project.
AlI've done is simply open with the version of Unity that was used to create it
Version 2019.1.14f1

And I am confronted with 5 LWRP compile errors in the console

I really need to get this project running again and would appreciate ANY troubleshooting tips!
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• Assets/LWRPSupport/LWRPBackgroundRenderPass.cs(4,42): error CS0234: The type or namespace name 'LWRP' does not exist in the namespace 'UnityEngine.Experimental.Rendering' (are you missing an assembly reference?)

• Assets/LWRPSupport/LWRPBeforeCameraRender.cs(3,42): error CS0234: The type or namespace name 'LWRP' does not exist in the namespace 'UnityEngine.Experimental.Rendering' (are you missing an assembly reference?)

• Assets/LWRPSupport/LWRPBeforeCameraRender.cs(7,55): error CS0246: The type or namespace name 'IBeforeRender' could not be found (are you missing a using directive or an assembly reference?)

• Assets/LWRPSupport/LWRPBackgroundRenderPass.cs(42,30): error CS0115: 'LWRPBackgroundRenderPass.Execute(ScriptableRenderer, ScriptableRenderContext, ref RenderingData)': no suitable method found to override

• Assets/LWRPSupport/LWRPBackgroundRenderPass.cs(8,18): error CS0534: 'LWRPBackgroundRenderPass' does not implement inherited abstract member 'ScriptableRenderPass.Execute(ScriptableRenderContext, ref RenderingData)'