Landlords will install Alexa listening devices and claim that entitles them to a higher rent.

I think the crucial question is whether the tenants can physically disconnect it.

Alexa for Residential will help people (including landlords) snoop on each other.

How about passing laws that forbid landlords from requiring tenants to tolerate microphones or cameras inside the property they rent?

Requiring tenants to use an "online portal" (which is likely to require running nonfree Javascript software and could make tenants sign away their rights) should be forbidden as well.