There are a couple companies working on 'cheap enough'(?) turbines in the GA size category. https://turb.aero/ https://turb.aero/ (latest news is from March 20

There are a couple companies working on 'cheap enough'(?) turbines in the GA size category. https://turb.aero/ https://turb.aero/ (latest news is from March 2023, not sure the company is still afloat?) https://www.turbotech-aero.com/ https://www.turbotech-aero.com/ Interestingly, the turbotech engines at least are recuperated engines, which is kind of unusual. But they claim it's necessary to get decent efficiency of such a small engine.