On personal experience, Trial breakthrough probability rewards are next to 0.
While there have been dry runs in the regular survival (where you get mostly runes, maybe 1-4 awaken mats), trial breakthrough is almost always just runes.
Maybe once or twice a week I'd get 1-2 awaken mats, but that's about it.
However, I take consolation that the practice room rewards can be quite nice sometimes so it balances out (if you take it as a sort of probability reward)