[Wonder Warthog]

"Admittedly, I only served on six ships. And, admittedly, they were Navy ships and not luxury liners. However, I just don’t see how that could be done."

Very easily. The heat/chill medium is central and runs off ship power. The liquid coolant circulates through the ship to heat exchangers in each room. Air circulation is a simple fan/duct arrangement from outside air and back, probably with some kind of particle filtration in the air loop. Zero possibility of bacterial/viral cross-contamination.

Navy ships have totally different requirements.

[dsc]

If a ship has a thousand cabins, that means a thousand fans, a thousand heat exchangers, and how many miles of pressurized pipe and air ducting.