ACE COMBAT 8: WINGS OF THEVE is now in Advanced Access, and while the single-player works the online play appears blocked on SteamOS / Linux.
As noted on the Steam page it uses Easy Anti-Cheat, which can be enabled to work on Linux platforms but it appears the developers have not done so. You can join a lobby, but when you go to enter a game it will just kick you out. We're now listing it on our dedicated anti-cheat page.
Hopefully the developer will enable it, but for now – don't go buying it on any SteamOS / Linux system if you plan to play online until we hear from the developer. GamingOnLinux has reached out to see if they do plan to sort it out, will update if they reply.
"ACE COMBAT 8: WINGS OF THEVE features a deep engaging campaign, promising to deliver the most cinematic experience yet in the series. The story puts players in the role of an ace pilot in an emotionally charged story of identity and duty, fighting for the survival of their homeland. Returning to the series’ legendary fictitious setting, Strangereal is now a world at war, with the nation Federation of Central Usea (FCU) occupied and its military shattered. With the prospect of war for survival as the only option, players enter the cockpit under the name Wings of Theve, taking on the role of a legendary ace with their name tied to Theve, the capital of the FCU, and becoming the symbol of hope for every citizen in their imperiled nation. Joined by a squadron of three allied pilots, theirs is a flight against all odds to repel the Republic of Sotoa’s vicious attack and reclaim their lost homeland."
While it's in Advanced Access, everyone else will get the game unlocked on October 1st at 10PM UTC.