I think it No longer posible to install throu market. But Just ask Mycroft by saying “hey Mycroft - install homeassistant”
Then he Will install the skill.
Lr you can install throu shell with
Mycroft-msm install homeassistant.
If you Are into making or Changng skills i recomend the Thia Ide skill wich installs a complet devolopment enviorement on your Mycroft device which can be accesed throu your Web browser.