Strongly related bug for 18.04 with an explanation of what is hanging but referencing plymouth's "splash" which this system doesn't use:
$ cat /proc/cmdline BOOT_IMAGE=/vmlinuz-4.15.0-56-lowlatency root=/dev/mapper/VG02-rootfs ro intremap=no_x2apic_optout no_console_suspend acpi_osi=! "acpi_osi=Windows 2013" -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1744370 Title: 'systemd-sleep suspend' hung after an abortive suspend/resume To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1744370/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
