"Failed to connect to bus: No such file or directory" when running systemd --user commands with runuser as root

[Dave Houser <davehouser1@xxxxxxxxx>]

I am having issues on my Ubuntu 20.04 system running systemd v245.

When trying to run `runuser -l mruser -c "systemctl --user status myservice.service"` I keep getting "Failed to connect to bus: No such file or directory" 

This does not make sense to me because I have the same set up on a RHEL 8.4 system running systemd v239, and I dont see this issue. I can run systemd --user commands as root with runuser with no issues. 

Here is the troubleshooting I performed. 

• tried running systemctl --user status myservice.service as mruser, command runs with no errors.
• I already checked loginctl for mruser, Linger=yes
• Checked to make sure there was a systemd --user process running with ps
• Logged into the user's account directly with separate ssh session, Then tried the same command as root in the original session, still same error.
• mruser already has export XDG_RUNTIME_DIR=/run/user/$(id -u) in ~/.bashrc
• Tried rebooting the system, still nothing.
• Deployed a new instance of Ubuntu 20.04, same problem on it. 
• Already read this post, was not very helpful.

I made a post about this you can find it here --> https://askubuntu.com/questions/1430191/ubuntu-20-04-not-allowing-runuser-to-manage-systemd-user-services-failed-to?noredirect=1#comment2491580_1430191

This seems like odd behavior so I am not sure why this is happening. Can anyone help?

- Dave