Ahead of the release of Mecha BREAK on July 1st, Valve have checked it over and given it a rating for Steam Deck and SteamOS. The release time depends on timezones though, seems like for the UK it will release at 4AM UTC on July 2nd.
This is an interesting one though, since it uses Anti-Cheat Expert (ACE). Anti-cheat causes all sorts of problems for Linux platforms, and Anti-Cheat Expert (ACE) especially is a nuisance since it appears to only allow Steam Deck / SteamOS devices, and blocks normal Desktop Linux distributions. This is something I specifically noted here on GamingOnLinux in my previous article when testing the game during the demo.
Valve rated it today as Steam Deck Verified and SteamOS Compatible.

Direct Link
Hopefully at some point we'll see less of this platform-specific enabling of anti-cheat for Linux. Especially because it doesn't exactly make any sense, it's no more secure on SteamOS compared with normal desktop Linux. Anyone can unlock the SteamOS filesystem do anything in Desktop Mode, it's a false sense of security. Thankfully, there's very few games that actually use Anti-Cheat Expert (ACE), with SteamDB listing a total of 20 games.
More about it:
After the Catastrophe, humanity harnassed the power of Corite—a mysterious carbon-silicon mineral driving rapid technological recovery. But its pathogenic nature and relentless spread threaten to consume Earth's last habitable spaces. In just decades, Corite is projected to engulf the globe. Humanity must find a way to preserve civilization before the countdown reaches zero.
Resist. Adapt. Escape. Or follow Corite's call and forge a new path.
Uncover the secrets of Corite and fight for the future! Join S.H.A.D.O.W., pilot third-generation BREAK Strikers, and deploy now!
Choose your mecha—assault, melee, sniper, reconnaissance, or support. Battle at breakneck speed across three action-packed modes: Ace Arena (3v3), Operation VERGE (6v6), and Operation STORM (PvPvE). Dodge beams, weave through explosions, and dominate the battlefield!

I wonder how until someone figures out the mechanism theyre using to check for the OS so we can all maybe go around it and pretend we're all SteamOS emoji .
I am