Admittedly I had not attempted deleting "in the box" apps in Catalina but I had done so in previous versions of MacOS without difficulty as apparently you had. So when I tried to delete Mail.app (which I do not use) I got
“Mail†can’t be modified or deleted because it’s required by macOS.
I remember seeing that pop-up somewhere along the line, but I"ve got no idea what elicited it. What did you do?
If you try to either rm or sudo rm an Apple app, Terminal returns a laundry list of every one of its individual components appended with "Read-only file system." (When you try to rm 19 apps at once, Terminal's output is about a mile long.)
...but there is no problem deleting other apps. Being of a curious nature I was interested to see what unique protections Apple had put on the "in the box" apps so I did a Get Info and discovered, to my surprise that "Mail" that appears in the /Applications folder is NOT in the /Applications folder but in /System/Applications along with all the "in the box" applications and utilities while third party apps are in /Applications.
So Apple hasn't locked down the /Applications folder rather the /System/Applications folder and all the "in the box" apps are there as well. I have no idea what the icon that appears in the /Applications folder is it does not appear to be an alias, but it may be a Unix hard link.
<snip> While I am not yet able to verify this, I believe the /System folder or at least much of its content is not even on the same APFS volume as the /Applications, /Library, and /Users folders. So there significant changes in Catalina that I was either unaware of or at least I did/do not fully comprehend all of the implications and/or implementation. (Emphasis added)
I addressed the new /Apps & /System/Apps format with
this screenshot, which I originally posted in my Activity Monitor thread as part of a similar discussion.
The part I highlighted in red is on the mark. You can verify it by looking at the results of cloning a bootable volume to another volume in the same container (with SIP enabled). And if you're really into digging, take a look at the difference between CCC's and SuperDuper!'s results of the same clone.
By the way, If I attempt to drag an app from /System/Applications to the trash all I get is a slashed circle and nothing happens. Not even a warning message.
Yup, and if you try to command-delete it you get ABSOLUTELY NO response.
