This is a bit of a highlight and something I hope we see more of in future. You can now be matched up with people across Steam and all major consoles in Rocket League.
I said before we would see Valve start talking a lot more this year, especially with the Epic Store being a thing and we're starting to see that now. Valve have put out a post giving some background on Steam and what's to come in future.
Tower Unite, a 'community-based virtual world party game' had a Linux version that was left in Beta since 2016 and eventually it broke. They've now removed it in favour of people using Valve's Steam Play.
Last Epoch, a very promising Action RPG that was funded on Kickstarter already supports Linux, and my recent interactions with their team have been great.