[KevinH]

@RaelIAK,

So there is no macOS crash report? No crash, just a spinning wheel? Have you tried just waiting a couple of minutes to see if a crash happens eventually. Mac OS crash reports are quite valuable in deciphering issues.

Does your system use multiple displays? If so, try powering down all but the main one.

Are you sure you have not corrupted the file permissions on your mac?

App Cleaner and Uninstaller are not software I would recommend in any way on a Mac. Mostly they are Adware.

Did you truly disabled SIP/Gatekeeper (again not recommended at all - unless you are a developer and understand unix security approaches) or did you just set your Privacy as I showed in my first reply?

Are you using a third party anti-malware/anti-virus application? Have you tried temporarily disabling that?

And finally have you tried removing all the old Sigil settings files to make sure they are not corrupted? To do that, try the following to start up with fresh preferences for Sigil.

Open Terminal.app and type the following commands:

cd
cd Library
cd Application*Support
cd sigil-ebook
cd sigil
mv sigil_v6.ini sigil_v6_ini.keep
mv sigil.ini sigil_ini.keep

Outside of trying those, I am not sure how I can help as your system setup is very non-standard if you truly disabled SIP/Gatekeeper (ie. your computer may have issues or be infected).

One other thing to try would be to create a new user on your system, log in as that new user, and try installing and running Sigil, just in case you are auto-launching something that is interfering with Sigil in your regular account.