I bought a T540 3 years ago that shipped with a Bay Trail processor. This processor was absolutely unusable on Linux due to this bug (https://bugzilla.kernel.org/show_bug.cgi?id=109051). Even setting max cstate to 1 resulted in regular freezes.
Not only would Lenovo not accept a return of the laptop, I could not even get them to update their Linux compatibility page to warn other users!
To this day:
- The cstate bug is not fixed, and running Linux on a Bay Trail processor will cause lockups
- Lenovo continues to recommend laptop versions that are flat out broken on Linux (https://support.lenovo.com/us/en/solutions/pd031426)
So be careful!