The default port of the GSA is either 443 or 9392 (depending on the permissions of the user running the gsad daemon or the availability on the 443 port) as described in GitHub - greenbone/gsa: Greenbone Security Assistant - The web frontend for the Greenbone Community Edition
If this is really a GSA (your package/installation provider might have changed the default port) then please have a look at the description in the thread linked below on how to overwrite the global/system-wide configured cipher suites and TLS version of GnuTLS to a (currently) more secure one from within the gsad daemon.
I’m closing this thread as a duplicate of the linked below to avoid that the same topic is spread over various threads. Please let me know if you want to add an additional note/remark in this thread and i could temporarily re-open it for this.
If you have further questions on the cipher topic please follow up in this thread: