I get it too, but on a fresh Kubuntu 20.10!
$ lsb_release -a Distributor ID: Ubuntu Description: Ubuntu 20.10 Release: 20.10 Codename: groovy
$ systemd-run --user --scope echo hello systemd-run --user --scope echo hello
$ journalctl -e janv. 04 14:33:01 7710-eezIT systemd[1525]: run-r455914ea041e4490a546761646fda345.scope: Failed to add PIDs to scope's control group: Permission denied janv. 04 14:33:01 7710-eezIT systemd[1525]: run-r455914ea041e4490a546761646fda345.scope: Failed with result 'resources'. janv. 04 14:33:01 7710-eezIT systemd[1525]: Failed to start /usr/bin/echo hello.
The logs are fulfilled of this kind of messages.
I get it too, but on a fresh Kubuntu 20.10!
$ lsb_release -a
Distributor ID: Ubuntu
Description: Ubuntu 20.10
Release: 20.10
Codename: groovy
$ systemd-run --user --scope echo hello
systemd-run --user --scope echo hello
$ journalctl -e 1e4490a54676164 6fda345. scope: Failed to add PIDs to scope's control group: Permission denied 1e4490a54676164 6fda345. scope: Failed with result 'resources'.
janv. 04 14:33:01 7710-eezIT systemd[1525]: run-r455914ea04
janv. 04 14:33:01 7710-eezIT systemd[1525]: run-r455914ea04
janv. 04 14:33:01 7710-eezIT systemd[1525]: Failed to start /usr/bin/echo hello.
The logs are fulfilled of this kind of messages.