This is from the nginx.conf in the cointainer..
Enables the specified protocols. Default is TLSv1 TLSv1.1 TLSv1.2.
# TIP: If you're not obligated to support ancient clients, remove TLSv1.1.
ssl_protocols TLSv1.1 TLSv1.2 TLSv1.3;
...but that shouldn't(?) matter since:
"The validation is performed when the container is started for the first time.
Nginx won't be up until ssl certs are successfully generated."
https://docs.linuxserver.io/general/swag