TBH, Galactic Union is a joke. Most of the perks you unlock are useless placeholders ( + flat unity...) and is just a generic crappy fed existing for ethics the devs seems to "dislike" for they always cripple them, nerf them, while they massively boost materialism.
So, Spiritualists and Hiveminds have to play with the GU crappy fed. This is even worse for Hives, because they don't have secondary ethic to unlock others Feds type.
Xenophobic ethics is converted by Hegemony Federation, I think.
IMHO, Federation is a really disappointing DLC, in a sense that it seems just unfinished, with too few fed types, crappy placeholders bonus for GU. As for the Galactic Council, the fédérations don't create that much narrative and engaging mechanic. Lots of modifiers on top of modifiers, you just wait for a XP slider to fill up to grab new modifiers...
And once in a while you get 5 lines pop up about some naval joint exercice (which don't exist IG, just text) or monument building project. Quite boring