In case you care, there is a retailer from Essex, that sells RYF-certified X200 and T400 with Libreboot and Trisquel pre-installed. [1]
Compared to professionally refurbished laptops of the same type (in Germany), the prices seem quite hefty, but if their prices for the service alone are an indication for the difficulty of the modification, then the hardware is actually a bargain.

[1] https://minifree.org/product-category/laptops/