Stellaris is one of my all time favorite games, but the late game really becomes unplayable from lag. I have over 1000 hours in it because I love it's modding and the immersion possible with it, but the performance is a real problem.
They have tried to address this too, with minor success, but that doesn't help when the start of each month from 2350 onwards takes seconds to load.
I use synphonium with my jellying server, works just fine.