How do I evade earthquake attacks from bosses?
Is "jump" too obvious an answer? You won't be flung if you're not on the ground when the shockwave activates, and you can stay in the air for a fairly long time with the jump-dash-jump bit. For multiple shockwaves, sometimes swift single hops can get you both in the air for the initial fling and over the shockwaves that approach from earlier attacks.
Of course, some bosses have very little telegraphing, but I suppose that's the challenge.