Theorising I've seen on this - though, I don't recall where - suggested targeting resonances with HAARP in a similar way to how a human singer can shatter a wineglass, by projecting the crystals frequency, causing it to oscillate itself to pieces.

That is high-watt transmission power may not be required. And further, it was suggested it's not done in isolation by HAARP but cooperatively with various transmitters also transmitting the same frequency at the same target - using standing waves.

It makes sense conceptually as an idea but I'm not sure there if there's any evidence of it?

The HAARP conspiracy theories are fun and date back to the old days of conspiracy theories when people wore tin foil hats and worried about government mind rays. Not at all based in reality or sensible but at least those conspiracies were harmless and non-political.

Anyway... no there's no evidence. But i do miss these classic conspiracy theories! Anyone remember the X-Files episode featuring HAARP?

So, the thing is tin foil hats do protect against the government mind rays; but aluminum foil hats don't. And too many people are wearing aluminum foil hats, and then the government mind rays work, and then they spout different conspiracy theories, planted by the government mind rays. And those conspiracy theories get traction, because they're spouted by people in metal hats.

It all comes back to the mind rays.