From postmarketOS Wiki

Some devices with an RTC wake alarm automatically turn on from powered-off state when they reach the alarm time. This includes, but may not be limited to, the PINE64 PinePhone. Some users may find this undesirable, especially if they use full disk encryption since the phone will power on to the osk-sdl screen and just stay there until the battery runs out.

The shutdown-clear-rtc-wakealarm package contains an OpenRC service that clears the RTC wake alarm. It can be enabled to run in the shutdown runlevel with:

$ rc-update add clear-rtc-wakealarm shutdown

 * service clear-rtc-wakealarm added to runlevel shutdown

Note that this service does not automatically restore the cleared wakealarm upon a reboot. It is expected that whatever set the wakealarm originally will restore it. The wakealarm is known to be restored by:

- gnome-clocks + waked, the combination used by Phosh.

See also

- pmaports#1970

- pmaports!3905