If I use Turtonator GX's Shell Trap attack:

Shell Trap - 20
During your opponent's next turn, if this Pokémon is damaged by an attack (even if this Pokémon is Knocked Out), put 8 damage counters on the Attacking Pokémon.
and during the next turn, my opponent attacks with a Pokémon that has a "prevent all effects of opponent's attacks" effect — let's say, for the sake of a non-hypothetical example, a Pokémon with a Metal Energy attached while Magearna EX is in play:

Mystic Heart
Prevent all effects of your opponent's attacks, except damage, done to each of your Pokémon that has any Energy attached to it. (Existing effects are not removed.)
does the Attacking Pokémon take damage in this case?

If you want to do some archaeology, this situation is almost exactly like the ruling on Sandslash (Mysterious Treasures) Spike Armor, but this ruling is very old and I don't know if it still applies (also it got reversed a couple times — and ironically I was the one that asked this back then! No wonder I'm having déjŕ vu...)