Never had an issue. You may want to turn off all of the bells and whistles that cause it to spike CPU when idle though, that might help.

Settings > Library > Enable 'Low Performance Mode'

Sluggish UI? I've never had issues with the UI being sluggish ..... Steam Chat always just works for me in the Steam client.

I've never had any problems with it tbh

I don't have any of these issues. My friends and I only use steam voice chat.

cant say I've had any of these problems with the chat. the voice chat does get choppy at times.

Still find it strange that the steam linux client performs that badly, you'd think with steam os they'd focus on knocking these bugs out but I've had vanishing context menus for years now, even in alt tab view