Manjaro KDE Plasma Suspend/Hibernate not working

Yes…

/**
 * register_nosave_region - Register a region of unsaveable memory.
 *
 * Register a range of page frames the contents of which should not be saved
 * during hibernation (to be used in the early initialization code).
 */

linux/kernel/power/snapshot.c at 349a2d52ffe59b7a0c5876fa7ee9f3eaf188b830 · torvalds/linux · GitHub

Maybe just add this:
file: /etc/systemd/logind.conf

HandleLidSwitch=ignore

and

sudo systemctl restart systemd-logind.service

This can be done here:
file: /etc/systemd/sleep.conf

AllowSuspend=no
AllowHibernation=no
AllowSuspendThenHibernate=no
AllowHybridSleep=no

That involves recompiling the kernel with the debug flag…

CONFIG_DEBUG_INFO=y

No idea, if you can do this, but there are a lot of tutorials… here is one on the forum:

Can you post this?

cat  /sys/power/state
cat /sys/power/disk