Can't open new X clients after 10 days logged in.
Description:
After 10 days logged in, systemd by default removes the xauth symlink from /tmp placed by sddm, causing $XAUTHORITY to no longer point to an xauth cookie, resulting in them not being able to open. This is a case of conflicting defaults, systemd expects files in /tmp not updated within 10 days to be safe to remove, while SDDM expects files in /tmp to never be automatically removed.
Possible solution:
I have read that setting the sticky bit on a file prevents systemd from automatically removing that file.
Additional info:
The systemd setting in question is found in /usr/lib/tmpfiles.d/tmp.conf (owned by systemd), as "q /tmp 1777 root root 10d"
Steps to reproduce:
Login using SDDM to an X session, stay logged in for 10 days. After 10 days pass, new X clients will no longer open.