The current Codex: Daemonhunters does not list the Land Raider Redeemer as a legal heavy support choice, nor as a legal inducted Space Marine unit (see the list on page 30 of the codex).
The reason they list the Land Raider Redeemer with the Grey Knights in the online shop is unknown to me.
There is actually a Grey Knight Land Raider Redeemer. However, it is from the supplement Imperial Armoury books (I forgot which one) and considered optional material such as Apocalypse or Planetstrike. If you want to use it in a regular 40k game, you need to get the permission of your opponent. Do note that it is slightly different from that of the LR Redeemer from the regular Space Marine codex (it has sponsoon incinerators and hull-mounted twin-linked psycannons instead of the standard Redeemer guns).
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