Plin

Thank you Mark, It worked fine after including source.list of Ubuntu 20. I appended the sources from https://gist.github.com/vczb/694d55169f67a3b2ad20df1385a3e983 to the end of /etc/apt/source.list on Ubuntu 22.04, then `sudo apt update && sudo apt install plasticscm-client-core` can be installed correctly