Source: vzctl Version: 4.9.4-6 Severity: serious vzctl needs kernel support, specifically the "vz" patches. Debian hasn't shipped those in a long time. By now it appears upstream development has moved back behind more closed doors, and it's unlikely we'll see anything for bullseye.
Also, IIRC, the RHEL8-based kernel trees would need newer tooling, not "vzctl". (Which also doesn't seem to be public.) Continuing shipping vzctl will not help anyone. I'll also file bugs against the related vzquota, vzstats programs. Chris