Some months ago, I ordered a Dommel SpeedConnect Plus connection. Since Dommel is using the network of the monopolist Belgacom in Belgium, I am forced to buy one specific type of VDSL2 router: Sagem F@st 3464. If you want to know why Belgacom forces this type of modem, you can find the report of the BIPT here, in English, Dutch or French.
Belgacom no longer uses theses modems for their own customers, but only resells them to ISP's using their xDSL network, so this is probably just a way for Belgacom to get rid of the Sagem's they still have in their stock.