I share your reservations about the plume pod. I don't know anything about the Deco, but I use a much more modest TP-Link Archer C6 with the Swish ONT with no probs at all, so I would expect that it should work fine.
While I don't have specific experience with the Deco X50, I am a Swish customer. Confirming that they use DHCP without any "options" or other complications, so you should be good to go (no need for PPPoE).
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