Download the free Onyx (https://www.titanium-software.fr/en/onyx.html), select the Onyx version for your OS, Catalina, download, run it, reboot.
In Onyx run almost everything in the Maintenance tab, deselecting things you may not want deleted, like Launch Services . Hit the "Options" button across from Internet and deselect more stuff like Cookies & Other Site Data, Browser History, Form Values, etc. (most of these are OFF by default). If you don’t know what something is, google it, or don’t run it, or ask me), then hit Run Tasks. After it's done it will ask for a reboot.
Also try to fix any directory damage by running Disk First Aid from Disk Utility: boot into Recovery Mode, (hold down Command-R when booting). When you're in Recovery Mode go to the Utilities menu and launch Disk Utility, say Repair Disk. When done go to Apple Menu for Startup disk and restart normally.(Also just doing a "Safe Boot" can clear out caches (restart, hold down shift until you see "Safe Boot" on the screen, let it fully boot, then reboot normally.)
Let me know how it works out.
- Version of Lightroom Classic
- The catalog location
- Did you update to MacOS 10.15.4 from 10.14.x ?
Latest version of Lightroom Classic (9.2) works fine with Catalina MacOS 10.15.x. We are not aware of the issue you mentioned.