Is it overtly criminal (in the US)? Or are any laws around recording in short-term rentals explicitly for hotels/motels (and Airbnb has a legal loophole)?

It definitely should be illegal to record people without consent when they're inside rented accommodation. I'm just not sure it is.

Seems to vary by state in the US; some states allow it with one party consent, and my understanding is that’s where the gray area is - if you are renting part of a home, can the owner consent on the renters behalf. Privacy is not well entrenched in federal law here.

It seems clearly morally wrong, even if the law does not (as usual) reflect the morality of the law's constituents.

In what context would it be reasonable to film a hotel (or cohotelling or whatever bullshit term they invented to dodge regulations) room without someone's knowledge? This is literal horror story shit. Perhaps people should be angrier at the state rather than the hotel app