When I try and open my 4.27 project in 5 using open a copy, it seems to convert everything OK but crashes on the loading sequence at about 93% when trying to open it. Subsequent attempts just to open the newly converted project result in the same crash. The log is quite cryptic, any advice on how to track down what is causing this to happen? (Yeah I am on a M1 Mac as well, no hate please. 
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maybe try the conversion on a pc or get a pc friend to do it.
If the project had c++, it could be your vistudio/win sdk
I suggest trying to do the same with a blank ue4 template
like third person template
and migrate your project to it
something in the level bp thats firing on load?
You also to have to make sure the project’s plugins are ready and or compiled for UE5, you might want to disable all the outside of Epic plugins in a copy of the project in 4.27. Also Epic is at war with Apple so using that hardware I consider a all bets are off option even though I think it is cool hardware I would never expect it to work as well or at all like trying to use Linux.
Just tried the same steps going from 4.27 to 5.03 using the new release and it all worked fine. So there must have been some issue in UE 5 that has now been caught as I did not change anything with the project. Anyway all good now.