From which Spectrum Version can OneClick use TLS 1.3?
Release : 10.4.x, 20.2.x, 21.2.x
Component : Spectrum OneClick
From the Broadcom Communities thread
https://community.broadcom.com/enterprisesoftware/communities/community-home/digestviewer/viewthread?MessageKey=21a15c61-caf8-4b25-8f1a-13ad00b71165&CommunityKey=671164c3-e575-4b08-96ab-edc2e1ceed13&tab=digestviewer#bm21a15c61-caf8-4b25-8f1a-13ad00b71165
TLS 1.3 was only supported in Java 11. But seeing it may have been back ported to Java 8 in 8u262-b10 from AdoptOpenJDK
Spectrum uses Apache Tomcat as a webserver. It appears Spectrum 10.4.3 ships OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_275-b01). So if you are running 10.4.3+, you might be able to enable TLS1.3.
From Spectrum 21.2.x documentation, the communication between OneClick and Spectrum application uses TLS 1.3 by enabling the secure CORBA. Refer to: