Same here. Like… forever now.
When I click “hibernate”/ “standby”, the PC goes off for a second, and then switches on again. Resetting the energy settings to default helped for some time, but that only made it a bit less often IIRC, not fixing it.
On my laptop, that doesn’t happen. I set it to go to standby if the lid closes, and it works as it should.
My thesis is, that there are different standby-states. KDE tries to force one explicit kind of it, and if the device doesn’t support it, it won’t go into standby properly.
On Gnome on the other hand, I never had problems with the standby on my PC. It’s a KDE issue
Grocy is exactly what you asked for.