On Lenovo ThinkPads you can switch the Fn and Ctrl keys using the Lenovo Vantage software.
- Download Lenovo Vantage from the Microsoft Store.
- After installing, launch Lenovo Vantage from the Start menu.
- From the top right menu bar click Devices > Input & Accessories.
- Scroll down to Fn and Ctrl key swap and click the settings slider to on (green and to the right).
- The functionality of the keys should swap once you close Lenovo Vantage.