I don’t know why SSH isn’t enabled by default on the official image but just found this in the HA logs on DietPi:
root@DietPi:/mnt/dietpi_userdata/homeassistant# tail home-assistant.log
ERROR: Command errored out with exit status 1: /home/homeassistant/.pyenv/versions/3.8.0/bin/python3.8 -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-_q5m_aur/pillow/setup.py'"'"'; __file__='"'"'/tmp/pip-install-_q5m_aur/pillow/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-9azgjm5z/install-record.txt --single-version-externally-managed --prefix '' --user --prefix= --compile --install-headers /mnt/dietpi_userdata/homeassistant/deps/include/python3.8/pillow Check the logs for full command output.
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Setup failed for image: Requirements for image not found: ['pillow==7.2.0'].
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Unable to set up dependencies of person. Setup failed for dependencies: image
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Setup failed for person: Could not set up all dependencies.
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Unable to set up dependencies of onboarding. Setup failed for dependencies: person
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Setup failed for onboarding: Could not set up all dependencies.
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Unable to set up dependencies of frontend. Setup failed for dependencies: onboarding
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Setup failed for frontend: Could not set up all dependencies.
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Unable to set up dependencies of safe_mode. Setup failed for dependencies: frontend
2020-09-19 13:29:16 ERROR (MainThread) [homeassistant.setup] Setup failed for safe_mode: Could not set up all dependencies.
root@DietPi:/mnt/dietpi_userdata/homeassistant#