How to configure MySQL 8.0.21 to use databases from 8.0.18 on macOS 10.14

Question

I upgraded MYSQL 8.0.18 to 8.0.21, on my Mac Mojave, using the release mysql-8.0.21-macos10.15-x86_64, which Oracle says supports Mojave 10.14...

Now I can\'t get MyS