Up until now, there have been few vendors to choose pre-installed Linux. IMO, the most usual thing is for people wanting to run Linux is to buy it with Windows pre-installed, boot it straight into a Linux install disk, and wipe off Windows - perhaps with the additional step of reclaiming the cost of Windows included with the purchase.
IINM, that won't be possible, so we need a 'none' option on the OS choice list before we buy it, then they don't install anything and just ship it directly to us.
In some ways, that seems a lot simpler, if we can get the likes of Dell, Lenovo/etc to do that. Maybe they will start selling more pre-installed Linux desktops - there have been some, but the choice was limited and there was always the 'wipe Windows' option.