I assumed it was rho (ρ) of hydrogen since rho is used for density...
RememberTheEnding
I added the repos to my existing arch install sometime last year I think. It's pretty seamless in that regard, I think I only ran into a mirror sync issue once, and it was resolved a few hours later.
My CPU supports the v4 packages, but I'm not really sure how much benefit there is for most things. (And things like tf/torch aren't coming from the repos anyways.)
I also use their kernel. I can feel a difference between stock and zen or stock and cachyos, but I don't think I'd be able to tell zen and cachyos apart tbh.
I definitely wouldn't switch distros for it, but since it's a trivial, drop in repo, I'll keep using it.
Adding another organization isn't ideal trust-wise of course.
Regarding the second point: applications change it. It's really annoying. I think Discord and Zoom both do it.
Given that you would need an exceedingly extensive, labeled dataset to start working with actions/behaviours/body language directly, the only realistic way to start would be with a language model. (And while these are sometimes decent, they're absolutely terrible at other times (and there's generally no way to tell which time is which).)
https://xkcd.com/2929/