Agreed. Maybe the external combustion engine too, I hear that Stirling-cycle engines can approach the power/weight requirements for flight....
I believe steam engines can do the job too, not as well as IC but well enough. There are problems to address, some of which can be solved technically with enough effort, others might simply be accepted
I like airships a lot but it is little appreciated that the same advances that made them practical were also what made airplanes practical; block the road to the latter with technical limits and you've blocked the road to the former too.
Ramjets are a good idea for going fast, at speeds greater than sound and above. They suck for subsonic purposes! Well, if you've got nothing better, I guess for some applications they might compete with steam engines. Particularly for applications where you need only a brief period of thrust; they will be murder on fuel consumption rates but they are lighter and simpler engines than almost anything. So a rocket takeoff, using storable (though toxic and dangerous!) hypergolic fuels (the rocket engine being about the only thing that rivals a ramjet for lightness and relative simplicity!) and ramjet flight (even the hideously low fuel efficiency of a ramjet at subsonic speeds is superior to the mass consumption rate of a rocket), accepting that fuel will be gobbled up hence endurance is low, might be workable. For most purposes even a mediocre IC engine, or a sophisticated steam or Stirling type engine, would be better. For missiles, though, the ramjet is attractive; I've thought of some wackier ideas too.
An option often considered but that rarely worked well in practice in WWII for instance was to land troops in gliders.
But suppose we have heavy gliders designed to fly quite fast, at nearly sonic speeds, and have a fleet of airships to drop them from, and they have ramjets? Now the glider pilot has some thrust to work with, and the plane is going fast, hence hard to intercept. If there is some method installed to enable a slow crash landing on a small pre-selected site, say a bunch of parachutes are deployed and rocket engines (like solid-fuel JATO types) are lit during landing approach for the thrust (once slowed down, the ramjets will cut off completely), then maybe we could do D-Day Buck Rogers style!
As for ornithopters, I just don't believe in them. I suppose today with our really high tech materials and computer control, we might manage to make some work as stunts, but they wouldn't serve any purpose we can't meet better with more conventional craft. I just don't believe someone with 19th century tech could make one work at all.