Having something work and you don’t know why is even worse than having it not work and you don’t know why…
Now let me shutdown and then try to suspend again after a restart… This machine is used to do actual work and thus should be most reliable.
I must also re-test the suspend-then-hibernate—would you know offhand where to set the hibernation timeout? (It’s supposed to react on battery level and a settable “in suspend mode for” time, as far as I remember.)
Never mind, found it. Set HibernateDelaySec=300 in /etc/systemd/sleep.conf for a test (it’s normally 60min on this system), and invoked systemctl suspend-then-hibernate.
All good, RTC wakeup functions, system suspends, wakes up after 5 minutes and hibernates. When powering on again, it resumes fine from hibernation state.
Love that functionality. If ever I just suspend my laptop and then forget it, it’ll auto-hibernate when either a) the battery goes below 5%, or b) the HibernateDelaySec runs out, whichever comes first.
Linux is indeed a very fine system to work with.