I realize most discussions on this probably happened months ago But recently I noticed that Tennogen items have indeed been showing up on my Discord Warframe client, for PLAT no less! Granted, it seems to currently only be the very first Tennogen skins (scindo, Magnus, etc.), but it gives me hope that sometime in the near future I might be able to get the rest of the Tennogen items there as well.
Frankly, I almost never buy Tennogen on my Steam client because I choose to support the game through frequent purchases of Prime bundles (9 plus the Founders bundle, if I remember correctly). It gives me a surplus of plat, and I really hate that I have to pay extra money for Tennogen items outside of the plat-ecosystem, just because of Steam's pricing mechanics. I'd much rather pay with the plat I've already bought, especially since I'm reaching the point where there is little for me to purchase with plat.
So, if you are reading this, oh random DE person, I love supporting your game (since the beginning) but please keep up the process of bringing over more Tennogen to Discord. So I can continue to support you in the way that helps us both.