I am using SY on a Mac with the M1, all software is up to date. SU keeps crashing, usually when I just close a file! This seems like a very simple task, I also had the same problem with the previous SU 2020 version on a different Mac.
There have been reports recently about such crashes. Search the forum and you can find ways to fix the installation that @colin has provided. The most common causes, if I recall right, are some bad files left behind from an earlier installation or trying to run SketchUp from the installer .dmg instead of properly copying it into Applications.
Those other cases would crash on launch, or when using materials. This is a crash when closing the file, and Mike has another customer file that does that. Hence the question about closing a simple template.
Moky seems not to have sent in a bugsplat yet, to see if it is the same as Mike’s case.
I use simple groups and components only. I do not use sketchy edges. Will send another bugsplasqh once it crashes. It is not consistent in terms of when it happens