In this document, I will explain how to upgrade the default systemd version from 237 to 242.
The main reason why I needed this was related to the DNS-over-TLS that was not supported in the version 237 but available from version 242.
Later, when playing with Lynis, the security auditing tool, I then discovered that the version 242 was also providing the command systemd-analyze that is used by lynis to detect if existing systemd services are configured correctly in the security context, meaning that the existing services can run as expected but needs few or several changes in their configuration to make them safe without any exploitable attack surfaces.
You can try it once you've installed the version 242 of systemd that way: