hi, welcome.
i have this issue in plasma 5 and i’ve heard that others in in plasma 6 have also experienced this “disconnect”
in kubuntu 22.04 there used to be a checkbox something like [ ] After some time hibernate and the time depended on your setting for HibernateDelaySec=3h in /etc/systemd/sleep.conf
but now in 24.04 that checkbox is no longer present and the delay setting no long has any affect.
so i have taken to writing a script and running that instead of relying on the plasma power settings to handle it.
see this recent thread on the topic…