More on: Security and Privacy pane crashing system preferences on Catalina

Okay; here you go...

Thank you. I uninstalled Avast using their uninstaller, restarted my Mac, ran EtreCheckPro again. It reported two remaining Avast “scheduling” files -- I wish I had recorded the names of them -- which I deleted, then restarted my Mac, then ran EtreCheckPro again, the report of which is attached to this doc.

After reading the article about Avast's unethical behavior (thanks for that info), I'm not going to reinstall Avast but am going to uninstall it on my Windows PC and iPhone. And I'll not renew when my trial period ends.

In the last couple of days I found that as long as I don't run BOINC, my Mac acts very well.

After having installed the Security Updates, I restarted the Mac in Safe Boot Mode, then tried again to launch the Security & Privacy System Pref. I got the same thing: spinning wait cursor, all of System Prefs becoming inaccessible, no way to get into Security & Privacy, forced to force-quit System Prefs (and still no way to get into Security & Privacy).

If your Mini works for you and you don't need whatever 10.15.7 offers, I'd definitely keep the status quo! I have no idea what the supposed advantages are of 10.15.7 over 10.13.6. I'm glad you're not having problems with your 2019 iMac.

Hello and thanks for the utility recommendations and for all of your help.

I spent a few hours gathering those utilities and doing various configuring routines and running the utilities and ended up with the following; I don’t know which ones you’d want to see:

1. EtreCheckPro Report with Mac in Default Mode

2. EtreCheckPro Report with Mac in Safe Boot Mode

3. Smart Utility Drive Report of my internal "Samsung SSD 850 PRO 512GB Media" drive

4. DriveDxReport of the same drive in #3 above (note: it was my main drive up until a few weeks ago when it suddenly developed horrible write speeds, I don’t trust or use it anymore)

5. DriveDxReport of my "SP SPCC Solid State Disk Media" drive which I use for backups (in addition to DropBox)

I have another drive, my "SanDisk Extreme SSD Media" drive which is my Mac’s main drive. I couldn’t get either app to give me a report on it, despite running the utility to add something that I don’t remember (a SMART driver?).

This Main drive and the Backup drive in #5 are both external SSDs which the Smart Utility app wouldn’t report on. The one internal SSD is the one I mentioned I don’t trust. USB 3.0 is fast enough for my external SSDs; I’m not going to mess around replacing the untrustworthy internal SSD.

My primary computer is actually a modern, very fast Windows 11 PC (despite my having owned and loved Macs since my first one, a new “Fat Mac” 512ke in 1986, back when an educational discount meant something). If I had the financial abilities now, I’d buy an Apple refurbished Mac mini to replace my old one.

Thank you. Yes, I'm quite certain as I tried the exact same procedure but applying the Security updates -- on at least three attempts -- and always came back to the original problem.