When connecting to MySQL, I get an SSL "unknown error number" error.

You may get a ERROR 2026 (HY000): SSL connection error: unknown error number error when you try to connect to MySQL or MariaDB with an outdated client that does not support TLSv1.2 or TLSv1.3.

To fix this error, upgrade your client to a version that supports TLSv1.2 or TLSv1.3. MySQL also supports many options for customizing connections.

For more details on MySQL versions and their supported TLS versions, see the MySQL Encrypted Connection TLS Protocols and Ciphers docs.