Lockdown: systemd-logind: hibernation is restricted; see man kernel_lockdown.7

Few days back, I ran dmesg on my terminal to see this line Lockdown: systemd-logind: hibernation is restricted; see man kernel_lockdown.7

Sometimes, as in the image below, the kernel ring buffer only prints this line repeatedly!

What is this diagnostic message regarding, and what does it mean? What should I be doing if it is something that I should be dealing with immediately?

The problem is that Linux with UEFI with secure boot requires a signed encrypted swap - which currently is not supported in Linux!

The bigger question is why does systemd-logind trigger this? It isn't trying to hibernate.

On my machine, this is particularly irksome since it leaves my keyboard unresponsive for up to 30 seconds when I first boot or resume from sleep (Kubuntu 20.10).

From the error message, the referred manual: man kernel_lockdown.7:

Certain facilities are restricted:
· Unencrypted hibernation/suspend to swap are disallowed...

That pretty much sums it up: enabling swap encryption should fix the problem.