I was curious if magnetrons are "limited" to microwaves, or a specific "bandwidth " or would they allow for higher frequencys such as xrays, etc?

 

Well, the frequency at which they operate is largely dependent on the geometry, so, in theory, no, they're not limited to microwaves. However, they'd have to be pretty small to generate anything higher (I don't have a dimension off the top of my head). With reduced size would then also come reduced power capability. For higher frequencies like xrays there are better ways of generating them (such as electron beam collisions or certain materials that just...emit them).

 

Whatever the operating frequency range of available magnetrons is, is likely the practical limit of the device, and no, that doesn't extent to x-ray frequencies which are way above that.
The inner magnetron inner dimensions are comparable to the wavelength of the frequency generated, which for a microwave oven is about 12.2 cm with a frequency of 2.45 GHz.
Xrays have a frequency of 10^16 to 10^20 Hz with a corresponding wavelength of 10^-6 to 10^-10 cm, which is obviously far too small to make a magnetron.

 

Xrays have a frequency of 10^16 to 10^20 Hz with a corresponding wavelength of 10^-6 to 10^-10 cm, which is obviously far too small to make a magnetron.

For perspective, 10^-8 cm is 1 Angstrom, or, roughly, the diameter of a hydrogen atom in its ground state.

 

Cavity (there are several types) magnetrons can be used to indirectly generate x-rays by RF acceleration of electrons.
https://ccah.vetmed.ucdavis.edu/sit...rces/pdfs/rad-onc-matney-x-ray-generators.pdf

I've not seen a magnetron cavity designed for the x-ray range anywhere but they can generate x-rays when operated at high power with high anode voltages but it's from wall collisions, not electrons crossing in EM fields.
http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/magnetron.html