Ahh it appears that Max’s download for it is broken now for some reason - and I actually don’t have the source for this old version anymore.
However, I have been slowly building a newer improved one (old one was in Python, new one is C#) which you can download and use here…
GD_Switcher.zip (1.7 MB)
This version might require that you have .Net Runtime 4.8 installed (if it currently isn’t on your system) so if it has any issues functioning correctly you might need to install that…
https://dotnet.microsoft.com/download/dotnet-framework/net48
Do note that the GOG side of things in it currently don’t work and only the Steam side functions correctly, sooo if you are using GOG you will have to wait a bit til I get around to that side of things.