I just rolled an older Mini from High Sierra to Catalina. What a mess! Keyboards don’t work, performance is in the toilet. It appears it’s burning tons of cycles doing security scans over /Applications. I have no clue what the problem is with the keyboard. (Neither wired USB Apple keyboard or 3rd party Bluetooth keyboard are working.) Reboot times are appalling…
If this doesn’t get any better in the next day, I’ll roll that machine back to High Sierra, and be damned to Catalina! (This is one of the worst upgrade experiences I’ve had in 35 years using a Mac…)