Oh yeah I was looking at Fluxer too, though haven't made an account yet.
In the "What's coming next" section on the website it mentions opt-in E2EE. So maybe it is actually on the roadmap? Unless the listed features aren't actually on the roadmap or I'm misunderstanding.
I hope it is anyway, I accepted no E2EE with Discord just because every single person I knew was using it, but I'm crossing my fingers to not have to make that compromise again if possible.
I'll probably give Fluxer a try as well then and give all three a go and see which one sticks, hell maybe I'll end up on more than one.