What do you think about waiting until https://github.com/dotnet/designs/pull/58 is implemented and using the config file?

I'm fine with that.

Question to check if this works as I think it does:

The dotnet.sh file is provided by the dotnet-host package, and as a result the host and the dotnet.sh file will be in sync.
So with a 2.x host package installed: dotnet.sh includes DOTNET_ROOT.
With a 3.x host package installed: dotnet.sh doesn't include DOTNET_ROOT, and the dotnet-host package also includes /etc/dotnet/xxx.

Sorry about dropping the ball on this.

The dotnet.sh file is provided by the dotnet-host package, and as a result the host and the dotnet.sh file will be in sync.
So with a 2.x host package installed: dotnet.sh includes DOTNET_ROOT.
With a 3.x host package installed: dotnet.sh doesn't include DOTNET_ROOT, and the dotnet-host package also includes /etc/dotnet/xxx.

I think your comment are 100% correct.

This PR still needs to be merged, right?

.NET Core 3.0 doesn't need it.

We need it to avoid breaking .NET Core 2.2 apps.

We can drop it when 2.2 is EOL.

Thanks! I have rebased it and included it with: https://pagure.io/dotnet-sig/dotnet-3-0/pull-request/3#