Could be candidate for the exiled/penal/prison thread!
No water/atmo doesn't necessarily mean none - just under the threshhold defined in UWP for a discrete number. Thus, can have 'pockets' more than big enough for the population.
Plenty of drinking water underground on earth - that's where most of our drinking water comes from. Extreme topology can mean vaccum at nominal 'ground level'... but community could live in a very (very) deep 'hole' in their local region. Natural materials may be loaded with easily extracted O2 - even natural reactors / lightning storms, etc. harvested for electrolysis.