The Mistral Engines G-300 (paid subscription required) is a multi fuel Wankel rotary engine.

Though the term “multi-fuel” means that it can run on both aviation (100LL) and automotive (87 Octane) gasoline, it’s spark ignited, though their web site states that they are working on Jet fuel capable engines.

Obviously there are fewer parts than a conventional piston engine, there are no conventional valves in a Wankel, but it still has a reduction gear, which was the major maintenance headache in the Thielert engine.