On an EpilykosOS box: put a file named dashboard-password.txt with the new password on its first line on the SD card's BOOT drive, then start the box. Or, on its console (or over SSH with sudo), run epilykos-reset-password.

Either way also switches off two-step sign-in, so you are not locked out.

With Docker: set SETTINGS_PASSWORD for the container and restart it. If two-step sign-in is on, also add RESET_TWO_STEP=true to the container's environment in docker-compose.yaml for one start, then take it out again.