You had another click to go
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help.suddenlink.com/inte ··· ist.aspxI can't say for absolute certainty, I don't work for SL nor do I know when the last time their list was updated. But for obvious reasons, they can't maintain firmware for every cable modem made. With that in mind, I can only guess that that would be the difference between compatible and prefered.
I can also on the other hand say though, that I for a few years ran a modem that wasn't even on the list oh another cable provider and had no problems. Your mileage may vary, but it's a safe bet that any recent, major brand modem should work without a hitch.