I use it exclusively as a progressive web app on Linux and it's not particularly slow, but it is buggy as all hell. Easily the worst rich text editing experience of any chat client I've ever used. Teams is without a doubt the worst piece of software I'm required to use on a daily basis

It is also possible that you don’t notice the slow downs?

Teams installed directly from the App Store or Microsoft on any device I own (high end windows/mac/ipad) devices are all terribly slow

I have used it at two different orgs (a university and a company) and it had the same issue on both. Perhaps your org has the settings figured out!