If you had run apk upgrade on a Phosh installation prior to 19 June 2023, you may have ended up with a system that starts up to a black screen on your next reboot. This has been fixed now, so it is safe to upgrade. However, people who were affected can run apk fix from ttyescape or ssh to resolve it.
This was caused by a file being moved from the Phosh package to the Squeekboard package without the Squeekboard package declaring itself as being able to replace files from the Phosh package.
Relevant issue: pma#2178