Holy shit, Ubuntu is $101 cheaper than Windows! It's finally possible to escape from the "Windows is cheaper than Linux because of crapware" quagmire.

Not sure what you're getting at. Security vulnerability?

Sorry, wrong link. www.dell.com/developers. Updated the parent too.

Still don't see ECC there on the 5520.

Search for ECC on that page. Some of them do. It is possible that their SKUs change with time. Currently, 3520, 7510 and 7710 show ECC support. Dell's site is quite terrible for navigation. You may have to spend some time to find the right model.

The point was to have the compact XPS-like casing. All those other ones are bulky. So I'd have to go with replacing the RAM myself... I really don't get why this configuration option is missing here.

It's not available for that model, but the 3520, 7520, 7720, 7510 and 7710 all offer ECC RAM as an option.

See my reply to the other comment pointing this out.