I sorted mine, it turned out to be partially self inflicted. I had cloned, using Migration Assistant, from old Macbook Air to new Macbook Pro. The first migration attempt failed, so I repeated it, twice more. This was finally successful, but meant that where I started with a username "john smith" which had a home directory of "johnsmith" I ended up with an Apple created username of "john smith 1 2" and home directory root of "johnsmith12" on the MacHD.
Several apps, including Skype, Zoom and Dropbox had a problem with that and did not correctly parse the spaces in the new username, and erase them to create the home directory they were looking for.
So I followed the Apple instructions on how to rename a username and rename the homedirectory root to get back to plain old "john smith". And then the problems got worse. Even Safari was failing to start up with a file permission error that I found in the log, and by working my way down the library tree correcting permission I got Safari working again. But i had no idea how to fix what I now think was a file permission error somewhere down the home directory tree in the system files. Meanwhile th old Macbook Air was working fine on the old diosk from which I had cloned the Pro.
I fixed it by - 1) Wiping the disk and reinstalling Mojave to clean disk, creating the old "john smith" user name, and then 2) using migration assistant to move all my files over from the old Macbook Air. This brings all the apps, and data folders to homedir "johnsmith", but does not the touch the OS. I tried all combinations of less radical approach, but it clearly needed a clean sheet. Now everything is working fine, and no file permission errors, privacy security works correctly and safari is fine. So for your problem, maybe backup everything to timemachine. Reload a clean Mojave, and then bring all the files back from timemachine.
The issue for Apple is that a file permission error, and a file not found errors are not getting reported as errors. When this happens privacy & security settings simply appear to work but do nothing.