My Systemd unit uses User=hass, but user is reasonably locked. su, sudo or runuser are not aplicable.
systemd-run --uid=$(id -u hass) --gid=$(id -g hass) /usr/bin/python -m venv /var/lib/hass/.venv && /var/lib/hass/.venv/bin/pip install packaging
systemd-run --uid=$(id -u hass) --gid=$(id -g hass) /usr/bin/python -m venv /var/lib/hass/.venv && /var/lib/hass/.venv/bin/hass --config /var/lib/hass/ --script check_config -i -f