I came across trouble with my WordPress site because dropbox hanged. I reinstalled everything and forgot the PHP problem I had earlier. I ended up wasting a day trying to figure out what happened again.
I still can’t figure out why php7.4 doesn’t work with the latest WordPress upgrade. Maybe something was wrong with the upgrade during the process. I ended up reinstalling WordPress and copy files without overwriting (cp -rn) and that appeared to do the trick. But now I have left two copies and still can’t figure out why one is not working. Will take another look again when I have more time.