ARMORED CORE VI FIRES OF RUBICON is the big new release developed by FromSoftware Inc, the same team from ELDEN RING and it does seem to run quite well on Steam Deck and desktop Linux.
The game does use Easy Anti-Cheat, however FromSoftware have it enabled for Linux / Steam Deck so that doesn't appear to be causing any issues. They said clearly before releasing they did want it to work well on Steam Deck so that's great to see. It's also rated Steam Deck playable by Valve, not Verified as some text is too small — an ongoing problem many developers still don't add in text scaling.
Here's a look at it on Steam Deck showing gameplay plus a little benchmark across Low, Medium, High and Max Presets:
For Steam Deck my choice graphics settings are simply the Medium Preset, with Motion Blur OFF and 40Hz locked on the Steam Deck. Overall that seems to be a pretty decent. While the "best" might be to lock it to 30FPS due to some drops in large battles, a lot of it can hit 40 so it just felt better to stick there overall. Like most bigger intense games, battery life is not long between 1.5-2 hours.
On desktop Linux (Kubuntu), running it on the Max Preset with my AMD Ryzen 5800x and Radeon 6800 XT it's been sticking quite well around 90FPS at 2560x1440. So I'm quite happy with the performance on this one. I did try for 120FPS, but on Max it would dip regularly between 90-100FPS depending on what was going on. This is without the setting to dynamically adjust the rendering, and there's no settings for any AMD FSR.
Desktop Linux screenshots (click to enlarge):
Two problems I did notice on desktop Linux: the first is that the Steam Overlay does not work with it but Steam Achievements work just fine though. The other is that while gamepad controls work perfectly, it will on some launches get stuck showing keyboard icons.
Something to keep in mind is that it is a tough game. Much like ELDEN RING, it will punish you. However, I feel the combat here is plenty more forgiving and personally, I much prefer the mech setting. Since it's mission-based, it works quite well to give you plenty of breaks.
Really seems like FromSoftware Inc. are onto another hit here. It won't get anywhere near the status that ELDEN RING had but I've no doubt it will sell well and be enjoyed by many.