Thanks for the reply. On the popup window about copying the project I chose More options… Skip conversion and it opened but seems to stop loading at 45%. I didn’t see this option at first.
Alternatively, I tried adding an empty folder named source to the projects directory and double clicked on the project file, which opens it but same problem with it freezing at 45%.
I just left the project to load, and 10 minutes of “initializing 45%” and it finally opened completely. Its still compiling 1000s of shaders, but at least I’m in UE4. Patience seems to be the key here.