Yes, it works surprisingly good. There is one Problem: The desktop layout of element is very unhandy on a small screen. The bar with contacts is always open, the chat area is so small, that you can’t even see any message. Yo need to rotate the phone, then it is possible but uncomfortable.
I think, Element is a javascript app, which uses the same code base for android, where a mobile friendly layout exists. Making it possible to use this mobile layout from the android app in the desktop version on pureOS could be an easy but effective step to use matrix on pureOS.