ps -eo lxc no longer shows a task's lxc container

[Forest]

When I use the ps command's "lxc" format specifier, for example:

ps -eo pid,lxc,command

The second output column is supposed to show "the name of the lxc container within which a task is running. If a process is not running inside a container, a dash ('-') will be shown." [1]

This worked fine until I upgraded from ubuntu 19.04 to 19.10, which brought me from lxc 3.03 to 3.04. Now, that column always contains a dash instead of the container name, even for processes that are running inside a container. The "lxc" format specifier seems to be broken now.

[1] https://manpages.ubuntu.com/manpages/eoan/man1/ps.1.html#standard%20format%20specifiers

[Forest (foresto)]

The top command's LXC column (not shown by default, but can be enabled through the 'f' menu) also shows a - for all processes, including those that belong to containers.

My containers are unprivileged, in case that matters.