Ableton Link released in 2016 (2015?). Many Link-enabled apps -- including Ableton Live itself -- can send MIDI clock based on Link. In my own experience in musical situations, Link beats MIDI Clock in every way: easy-to-use, reliable, and flexible.
So, in 2021, we implemented Ableton Link (and control loopers!) in MIDI Designer. Check out our Q&A Post on MIDI Designer and Ableton Link.
Note: we did promise in 2013 that we'd eventually implement MIDI Clock, but times have changed and Link is amazing and here to stay.