This seems to be caused by Focal's 5.4 kernel: after booting Ubuntu 19.10's linux-image-5.3.0-40-generic (5.3.0-40.32), which remained on the system after upgrading to 20.04, hibernate-disk (and resume afterwards) works fine.
** Also affects: linux-5.4 (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1866984 Title: linux-5.4 regression: hibernate-disk resumes instantly To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/hibernate/+bug/1866984/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs