Where do the 3* yellow evo shards drop? Secret Dungeons? What level? Normal? Hard? Madness?

I need only one shard and now I have to wait for the next Gunner Timerift??? Wait every 3 days for the highest secret dungeon???


Hey, developers! We need more information about droprates and new ways to get evo shards. I got so many 2* shards and got nothing to do with them! What about level up shards? 50 2* to get 1 3* f.e.?