Thanks for trying that, @taste.misrule.
I recommend restarting your machine after running softwareupdate --install-rosetta --agree-to-license
.
If that does not help, also try removing the MySQL 5 directory:
rm -rf ~/Library/Application\ Support/Local/lightning-services/mysql-5*
Then restart Local, remove the old MySQL 5 site you tried to run and create a new site with MySQL 5 to force it to redownload.