Comment 10 for bug 1872541

ssl-mode should default to a mode that tries to autodetect server support, with automatic fallback to disabled(PREFERRED, per https://dev.mysql.com/doc/refman/8.0/en/connection-options.html#option_general_ssl-mode), but I'm not sure if that works properly with the Aurora server.

Have you looked at https://aws.amazon.com/premiumsupport/knowledge-center/rds-error-2026-ssl-connection/?

The error message you get doesn't quite match what is mentioned there or what MySQL would report if the problem was that the client tried to enforce ssl, but I did find https://github.com/microsoft/msphpsql/issues/1023 which also mentions it working in 19.10 but no longer in 20.04. Maybe something related to openssl 1.1.1f?