"sole inhabitant" refers to being the only person or creature living in a specific place. It means there is no one else residing there except for that one individual. Full definition
Soon they discover what they think is an uncharted paradise, but is actually a dark, dangerous world — whose sole inhabitant is the «synthetic» David (Michael Fassbender), survivor of the doomed Prometheus expedition. (thewrap.com)
The official synopsis: Bound for a remote planet on the far side of the galaxy, the crew of the colony ship Covenant discovers what they think is an uncharted paradise, but is actually a dark, dangerous world — whose sole inhabitant is the «synthetic» David (Michael Fassbender), survivor of the doomed Prometheus expedition. (halloweendailynews.com)
Unless you are the sole inhabitant of an island, chances are that there are people around you who you could call upon to help you feel good about yourself and support you in your wellbeing endeavours. (womenshealthandfitness.com.au)