One of my favourite comic artists ever. His comics are equal parts bleak & funny. Found at https://pbfcomics.com/comics/the-talk/
Maybe they have like an underground greenhouse with artificial light and irrigation
That was my next thought, but then where do they get their power, water, and oxygen?
I suppose it could be like a “reserve the surface room for a day” kind of thing, and hundreds of people live down below, with enough space for greenhouses and algea pools for oxygen production. Geothermal power, or simply a solar farm out of view, and deep underground natural water reservoirs…
I still think the immortal people in an indestructible house is probably the best bet.