Hello Ari !
Thank you for posting on Microsoft Learn.
If your Azure Database for MariaDB Single Server is now disabled because of the retirement, the workload and its data are deleted at retirement and aren’t recoverable. That’s why connections now fail since the server DNS no longer resolves.
https://learn.microsoft.com/en-us/azure/mariadb/migrate/whats-happening-to-mariadb
You can check your own storage for prior exports, any mysqldump/mydumper files, DMS migration staging, ADF copy sinks, app side replicas since those are often the only remaining sources.
What I can recommend is that you reach out to Azure Support ticket for better assistance.
Ask for escalation to the product group for post retirement data recovery for Azure Database for MariaDB. There’s no guarantee, but support is the only path at this point.