For it to be buoyant, density would have to be less than air. If we’re holding to conservation of mass, then the bottle would have to be significantly larger than the paladin, which doesn’t sound particularly stealthy.

If there are in a sealed container that wouldn’t matter, unless it flies using a magical force without an equal and opposite force, at which point you might as well just throw out conservation of mass.

Bulldogs have trouble breathing because of their noses, right? Do you know if this helps or hinders that?

The website seems to work fine for me, but they seem to only support open hardware (e.g. Raspberry Pi or Mycroft). That doesn’t mean it wouldn’t work on other things though, especially with open software, but I wouldn’t be surprised if Echos require updates to be signed by Amazon, so it might require some hacking.