yes, many times. as you would expect, it obviously doesn't work.
.
> Using gyrotrons to generate enough microwave power to cut and weld glass has supposedly been tried. The company that was doing it seems to have disappeared.
that's correct. they weren't able to cut two inches of well controlled non-porous dry material.
.
> You'd expect industrial applications first.
honestly, you wouldn't. it's technical nonsense. lasers are more efficient and easy to build.
the reason we use microwaves to cook is they pass through most material harmlessly, and mostly interact with the water.
which is kind of a dealbreaker here.
.
> So, drilling with some kind of energy beam looks worth the trouble.
no, it's really not. it's just science fiction bs.
if we want to save the planet, just build regular 1970s nuclear power, and quit it with the "i'll invent something new with less than ten years on the clock" stuff.