Ubuntu 21.10 Systemd To Finally Ship With Cgroup v2 By Default
Upstream systemd has been defaulting to it for a while and other Linux distributions -- including Debian for which Ubuntu is based -- have been safely using it as well, but Ubuntu has been late to the party.
Ubuntu has been sticking to the legacy cgroup v1 hierarchy because their prized Snap support hasn't supported Cgroup v2. Upstream Snap still doesn't have the support yet but there are patches pending that are still expected to be merged this cycle. Thus Ubuntu is moving ahead before the 21.10 feature freeze for the systemd enabling of the unified/cgroupsv2 hierarchy support.
Details on this long overdue change via the Ubuntu mailing list with their advance notice on the change posted today.