@User: You can get a sense of how I have been doing Monte Carlo simulations with xschem, ngspice, and the sky130 PDK from some tutorial videos that I made for my mixed-signal VLSI class this semester:
Xschem / Ngspice Tutorial Showing How to Prepare Your Installation for Monte Carlo Simulation▾
,
Xschem / Ngspice Inverter VTC Monte Carlo Simulation Tutorial▾
,
Xschem / Ngspice Resistive Voltage Divider VTC Monte Carlo Simulation Tutorial▾
, and
Xschem / Ngspice R-2R Ladder DAC Transfer Characteristic Monte Carlo Simulation Tutorial▾