I just released the new MVVM Light preview version for .NET Standard 1.0. I also published an article in the MVVM Light documentation describing the installation of the .NET Standard 1.0 version of MVVM Light as well as the changes needed to existing applications.
Hopefully you find this helpful.
This is a pre-release version and I am eager to hear your feedback. If you have any issue during the uninstallation process, installation process or while using MVVM Light for .NET Standard 1.0, send me an email at Laurent@galasoft.ch for assistance.