what I did in the following order:
1.) Copy my complete GC folder from old machine to new machine
2a) Download Developer Release 3.6 from GoldenCheetah.org (altough there it reads June 2020 and I guess I had a later one? But not the Snapshot, maybe I used a link from this group).
2b) Open GC 3.6 for the first time (and the first GC on that new machine). Got prompted to make a new user first thing. Made a user named "dummy" and didn't do anything with it.
2c) navigated to the preferences and there to the first Tab "Allgemeines" (in German) and pointed athlete and workout library to my GC directory
2d) unsure about the exact course of next events. I guess I had to close GC, open it anew, got prompted for the sole athlete there is in this directory, i.e. me. Selected it and then the fans went on and GC was shown as "not responding" in the activity monitor. But ingested all activities just fine after some minutes of fan blaring.
So no - no Backup. Just a normal GC folder and a fresh "install" on a new machine.
3a) Downloaded the 3.6 snapshot from the 27th of December. And just copied it over into the programs folder over the former 3.6 June or Nov Developer Release.
3b) opened that incarnation for the first time. Hadn't to select an athlete, had'nt to point to the library. Ingestion took place. GC stayed responsive, a progressing progression bar could be followed on the top area under the menu bar like shown in the first screen shot. Fans were maxed out from the get go.
So yes, the latest snapshot solved the "not responding" issue but it may still have some issues left over which may lead to that behaviour? Granted, it runs under Rosetta 2 and all but... as does 3.5.
4a) renamed GoldenCheetah to GoldenCheetah36 in my programs folder
4b) downloaded 3.5 current stable release and installed it.
4c) opened 3.5 for the first time on the new machine. No need for selecting an athlete. Program started with ingesting all 1500 activities. With the progression bar progressing (just like the former snap shot 3.6 version) and subjectively quicker, with higher shown CPU usage (see screen shot) and no fans at all.
Hope this helps. :)