This proof of concept engine was running back in 2017: https://www.youtube.com/watch?v=FEn1iCU6Hh0
Yes, lots to prove but that's why they're building the -7.
If nobody ever tries anything new, we'll still be using basically the same stuff as we were in 1950- 75 years on. That doesn't seem like progress to me.
I count 3 new small turbines close to entering the market now. That's cool in my book. I hope at least one succeeds, as lots of hard work, money and thought went into each of them. I say sit back and see how these perform in the coming months/ years.
I applaud the dreamers, engineers and risk takers (financially) here.