I'm Fedora 28 user on a Lenovo Thinkpad X1 Carbon 6th generation which does not
support the S3 state out of the box. I found a patch and followed the following
introductions in order to apply the patch and it worked for me.
The arch wiki has a whole page on problems and fixes regarding the X1 Carbon 6th:
From there I followed these instructions and applied the refered patch:
In addition to the post to persist the changes when upgrading I updated in the file
/etc/grub.d/10_linux the line setting initrdefi to include /acpi_override.
The patch is working for me and I'm happy to have S3 support now.
Maybe this could be helpful for others and be shipped with the next kernel release.
With best regards,