cinnamon-settings запускает lightdm-settings с pkexec при этом сам запущен через pkexec.
Это приводит к конфликту.

Нужно запускать lightdm-settings без pkexec.

Логи предоставляю:
lightdm-settings через cinnamon-settings:
Oct 02 04:37:55 5-92acad polkit-agent-helper-1[7233]: pam_tcb(polkit-1:auth): Authentication passed for root from altlinux(uid=1000)
Oct 02 04:37:55 5-92acad polkitd[2058]: Operator of unix-session:1 successfully authenticated as unix-user:root to gain ONE-SHOT authorization for action org.freedesktop.policykit.exec for unix-process:5804:102693 [cinnamon-settings] (owned by unix-user:altlinux)
Oct 02 04:37:55 5-92acad pkexec[7227]: UNSPECIFIED (__progname="pkexec" uid=1000 euid=0): pam_tcb(polkit-1:session): Session opened for root by altlinux(uid=1000)
Oct 02 04:37:55 5-92acad pkexec[7227]: altlinux: Executing command [USER=root] [TTY=unknown] [CWD=/home/altlinux] [COMMAND=/usr/bin/lightdm-settings]
Oct 02 04:37:55 5-92acad pkexec[7239]: pam_tcb(polkit-1:session): Session opened for root by altlinux(uid=0)
Oct 02 04:37:55 5-92acad pkexec[7239]: root: Executing command [USER=root] [TTY=unknown] [CWD=/root] [COMMAND=/usr/lib/lightdm-settings/lightdm-settings]

lightdm-settings запущен напрямую:
Oct 02 04:39:07 5-92acad polkit-agent-helper-1[7277]: pam_tcb(polkit-1:auth): Authentication passed for root from altlinux(uid=1000)
Oct 02 04:39:07 5-92acad polkitd[2058]: Operator of unix-session:1 successfully authenticated as unix-user:root to gain TEMPORARY authorization for action org.x.lightdm-settings for unix-process:7268:149617 [/usr/bin/python3 /usr/bin/lightdm-settings] (owned by unix-user:altlinux)
Oct 02 04:39:07 5-92acad pkexec[7271]: UNSPECIFIED (__progname="pkexec" uid=1000 euid=0): pam_tcb(polkit-1:session): Session opened for root by altlinux(uid=1000)
Oct 02 04:39:07 5-92acad pkexec[7271]: altlinux: Executing command [USER=root] [TTY=unknown] [CWD=/home/altlinux] [COMMAND=/usr/lib/lightdm-settings/lightdm-settings]