I found this oscillator circuit used in the
LEAP#182 PowerSupply317Kit.
It is another variation of the basic Schmitt Inverter Waveform Generator pattern, which I tested in
LEAP#022 SchmittOscillator.
But performance … is quite terrible actually. Oscillation is only sustained for a small sweep of the 100kΩ pot.
The waveform is also heavily asymmetric - with a duty cycle at most 25%.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub