Unknown.
I think you won't know if it WILL work by looking at these references -
rather, they are good only for determining if it will NOT work. e.g.
there are components (thinking of the BIOS) that should, but may not
facilitate all of the desired features.
- Perhaps you can convince a Dev to create a "test USB stick" that will
boot and actually test and confirm suitability.
- Alternatively, some eager beaver will likely provide a report re:
T420s i5 to the HCL (the primary guide) by mid-October.
IMHO, it is best to wait for one of these.