Just tested, and can confirm backporting e8cf09b2a2ad0d48e5493050d54251d5f512d9b6 to focal's systemd fixes the segfaults when using machinectl shell on a Jammy host trying to start a shell in a Focal nspawn container.
Just tested, and can confirm backporting e8cf09b2a2ad0d4 8e5493050d54251 d5f512d9b6 to focal's systemd fixes the segfaults when using machinectl shell on a Jammy host trying to start a shell in a Focal nspawn container.