Thank you for the help, but we finally found the issue.
I had removed the /var/lib/mysql-files and /var/lib/mysql-keyring directories because they were empty and I found them annoying because they interfered with using the TAB-complete functionality.
I had run journalctl -xe (as the systemctl start error message suggested, but there was no mention of mysql-files), it wasn’t until a colleague ran journalctl -r that he found:
2022-02-23T08:48:10.646329-06:00 0 [ERROR] Aborting
Feb 23 08:48:10 wg9plmsqmd01.pblipa.ca mysqld[14710]: 2022-02-23T08:48:10.646194-06:00 0 [ERROR] Failed to access directory for --secure-file-priv. Please make sure that directory exists and
Feb 23 08:48:10 wg9plmsqmd01.pblipa.ca mysqld[14710]: mysqld: Error on realpath() on ‘/var/lib/mysql-files’ (Error 2 - No such file or directory)
Replacing the directory with the proper permissions appears to have worked.
Do you have any ideas why the mysql-files and mysql-keyring directories are needed?