new iMac 27, Safari suddenly quits as it opens, what next?

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

Hey COF2022,

It sounds like you're having an issue with Safari crashing on launch. We can understand wanting to look into that further. We want to help.

We'd recommend trying the steps in this article: If an app on your Mac stops responding, closes unexpectedly, or won’t open

Thanks!

Please download and run EtreCheck, and share the report to the clipboard. Then open a new reply here, and press the button that looks like a printed page (additional text, text attachment), and past the hardware and software configuration report into the text input box. From that data, we might be able to identify the issue.