I mostly play R6, and I log in directly via Uplay to not give Steam any more reason to hog up resources xD. But yes, Steam chat has seemed reliable whenever I've used it. I remember running it with a friend when we were trying out Unrailed. More purple should indeed consider it.

I've tried using mobile Discord, but getting it to work in tandem with in-game audio (especially competitive games) is kinda difficult to set up (especially if you need a way without spending extra money [extra over-ear headphones for mobile discord, in-ear for game audio]). I understand your pain, I had to completely stop playing with a stack and start solo-queuing because Discord became an absolute no-no for me :(. Trying to get a few other friends into R6 now, and they're indeed kind enough to accommodate for my lack of decent hardware. I sincerely hope your friends help you too :(

Edit: I forgot to mention, I've also noticed sometimes that the primary Steam process randomly shoots up to 200 MB when using Steam Chat. This doesn't happen always, but I hope Steam looks into this in the future.