I won a gambit game (regular, not prime) with the gear in the pic (namely trust, bygones, bad omens and the full ancient apocalypse armor) and the game is still saying I haven't completed the Dark Age Arsenal triumph and it's the only thing in the way of me getting the title of Dredgen.
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Yes, bugged. https://www.bungie.net/en/Forum/Post/251164099/0/0