There's a French startup that makes some pretty cool turbine range extenders for the general aviation market. Great power to weight ratios, and they come with the maintenance benefits of microturbines, which only have a single moving part. I can't remember exactly, and they don't have it in their specs, but I think they even use gasfoil bearings which means there is no need for oil lubrication.

https://www.turbotech-aero.com/index.html