To estimate ENGIE’s 2022 FFO / Net debt ratio using an S&P-style approach:

1. **Estimate FFO (Funds From Operations)**  
   A practical approximation is to use operating cash flow before working-capital movements, less cash taxes paid.  
   From the data:
   - Cash flows from operations before changes in working capital: **€12.415bn**
   - Income taxes paid: **€1.504bn**

   Estimated FFO:
   \[
   12.415 - 1.504 = 10.911 \text{ bn}
   \]

2. **Estimate net debt**  
   Use gross borrowings less cash and cash equivalents:
   - Long-term borrowings: **€28.083bn**
   - Current borrowings and current portion of noncurrent borrowings: **€12.508bn**
   - Cash and cash equivalents: **€15.570bn**

   Gross debt:
   \[
   28.083 + 12.508 = 40.591 \text{ bn}
   \]

   Net debt:
   \[
   40.591 - 15.570 = 25.021 \text{ bn}
   \]

3. **Calculate FFO / Net debt**
   \[
   \frac{10.911}{25.021} = 0.4361
   \]

   So the estimated FFO / Net debt ratio is approximately **43.6%**.

<answer>43.6%</answer>