An addon for .Net Core runtime 2.1.0 should be available soon from the LibreELEC Add-ons repository.
In the meantime, you can download a preview of the addon attached to this post.
To run the .Net Core runtime, install the addon and type `le_dotnet` at the console.
Emby will be switched from Mono to .Net Core.
You can download a preview of the Emby (18.104.22.168) for .Net Core addon attached to this post.
To run the Emby addon, first install the dotnet-runtime addon, then the Emby addon.
Emby listens at libreelec.local:8096.