Do you believe that energy (however or whatever you wish to call it or define it) cannot propagate through a vacuum?

You are framing your question from a viewpoint of utter misconception. THERE IS NO SUCH THING AS ENERGY. A mass in motion has: mass and velocity, upon collision with another mass one mass may decelerate and the other may accelerate and momentum is transferred - one mass has a reduced velocity and the other has a increased velocity. Force is the process of collision, the process of the transfer of momentum. One mass did work the other mass "received" work. A mass in motion is able to perform a limited amount of work, and this amount of work may be calculated based on mass and velocity and by making an assumption of the maximum amount of "momentum transfer through collision" (force) that could possibly be achieved given the initial mass and velocity. ONLY objects with mass have energy, since energy is an abstracted calculation from mass and velocity - energy is only a number, the result of a calculation.

"Energy" cannot propagate anywhere, it can only be calculated from mass in motion - see above for a physics rather than a supernatural explanation.

then how does a 'radar wave' propagate through a near-vacuum?

There are only two possible answers to this. One involves mass in linear motion, such as would be the case for a photon particle - a radar photon. The other is for mass in motion perpendicular to the wave motion, such as would be the case for a "radar wave", where at times the arrival/absorption of the wave momentum may be perceived as a photon. In both cases there is mass in motion. The radar photon has a frequency of 50Mhz-100Ghz, so using h and 1/2mv^2, it has a mass of 7.37x10^43kg to 1.47x10^39kg. It is either a particle that travels through the quantum aether field or a wave in the aether.

The detailed nature and operation of the aethereal substrate is indeed open for speculation and discussion, but, even allowing for the odd electron or proton here or there, the vacuum is far from empty