Hi I followed the steps to migrate from HL2 to ML2, upgraded MRTK to 2.8, as well as the unity editor to the most current supported by ML2.
I get about 72 error messages in the console most appears to be assembly with name .... already exists
These errors usually mean that there are duplicate assemblies in your project that conflict with each other. This can happen when you import MRTK packages without deleting the previous versions, or when you have other packages that depend on MRTK assemblies.
To fix these errors, you need to remove the duplicate assemblies from your project and make sure you only have one version of each assembly. See the official documentation for updating from earlier versions of MRTK.