So, instead of selling PCs, vendors should advertise their equipment as bundles:
-- "Behold! The new ASUS this-and-that PC plus Windows bundle!"
-- "Do you have ASUS this-and-that PC plus Linux?"
-- "Oh, we only sell PC-Windows bundles, sorry"
-- "Then I only want the PC."
-- "Then go to a PC vendor. This is a bundle vendor."
Problem solved.