Mariadb does not have a web interface. Try to access the database in a different way, for example connecting a bash shell to the container.
The message is OK, it seems like a telnet to test the app(the app is running(up), and the port is open(reachable)), but if you need to inspect your MariaDB database, you need to use any console client or programs like DBeaver or any web interface like PHPMyAdmin platform or something else.
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