It's mainly running the Disk Utility. I don't know if it's the late 2013 iMac or what else I'm doing wrong but ever since upgrading to Catalina I routinely get problems with adblocking programs and the browser. Opera and Brave function the best but Safari is the most problematic.
I know I've seen stuff about Safari on Big Sur but I'm wondering what the big differences are going to be? And am I going to have the same (or worse) problems with adblocking?
When you "upgraded" to Catalina, what OS did you "upgrade" from? And did you do a clean, fresh installation of Catalina, or did you just upgrade in place? Myself I did a clean, fresh installation. No issues at all.
Disk Utility is not bad, but it would be good if you do some disk cleanup on your own. Also, the excellent free program Onyx is a solid, reliable performer:
OnyX is a multifunction utility that you can use to verify the startup disk and the structure of its system files; run cleaning and computer maintenance tasks; configure some hidden parameters of many Apple applications; and more.
www.titanium-software.fr
Notice that link is specifically for Catalina, and it is the latest version of Onyx. As usual, I did my additional weekly disk cleanup/maintenance/repair, and backup, tasks yesterday on both of my Macs running the latest version of Catalina, OS 10.15.7, and that new version of Onyx, as expected, functioned flawlessly. I also use the excellent commercial program Tech Tool Pro for more extensive cleanup/maintenance and (rarely ever happens, but good to check) repairs.
Is there a specific reason why you use Safari? I see no need for it, and I do not have issues with Brave, Firefox, Google Chrome, or Opera, although I use Brave about 98% of the time, Opera for about 1 1/2%, and the other 2 for 1/2 %. Never had an issue. Of course I insure to always run the latest version of each.