The top XOR is acting in linear mode as an integrator the bottom XOR functions as a Schmitt trigger. Simple resistor and LED waveshaper provides an approximately sinewave output ( should probably be buffered )
UPDATE: using a real XOR cd4070ɓ the circuit was unstable producing unwanted oscillations, would be better to use 4049UB or 4069UB, must be UB version, otherwise the same stability problem is likely to recur. (27DEC2023)
