Is it possible to have multiple MySQL/MariaDB instances on Plesk for Linux?

Plesk does not support such functionality.

There are two possible alternative solutions:

• Set up an external MySQL/MariaDB database server in Plesk
• Use a Docker container to host separate MySQL/MariaDB instance in Plesk and add it as and external SQL database server using IP address 127.0.0.1 and the external Docker port.