Nice to see more bigger publisher jumping in to get their games working on Steam Deck and desktop Linux. Ubisoft has now upgraded For Honor to support Easy Anti-Cheat on Deck.
Published in their July 27th update it notes:
Updated Easy Anti-Cheat client module and library.
Developer's Comment:* This update of Easy Anti-Cheat makes the game playable on Steam Deck.*
Thanks to that, Valve also ran the game through verification bumping it up to a Steam Deck Playable rating with Proton Experimental (as seen on SteamDB) as it was previously Unsupported. It's Playable now and not Verified as Valve notes it still has issues with a launcher, it can show non-Steam Deck controller icons, you need to manually bring up the on-screen keyboard and it doesn't close properly so you need to force-close on it.
So Ubisoft have done the bare minimum to make it work. Hopefully they will also address the other issues to get it bumped up to Verified properly.
Trying it myself: it did initially get completely stuck sitting on a Uplay "Looking for patches" screen for a long time. Closing and reopening then just fixed it and it did it almost instantly. Logging into to Ubisoft Account also did need the touchscreen and manual on-screen keyboard (STEAM + X). After that logging in worked just fine, although it then gave me the full Ubisoft Connect app instead of launching the game. Closing and re-opening it then asked me for a CD Key, which is apparently a problem for many people and even more people even though it's supposed to be having a free weekend.
So, for science, I purchased the game. Thinking that would give me the needed key. Apparently that doesn't work either and I am also not alone in that problem. Seems they're having problems with their CD Key server so it may very well be supported on Steam Deck now but any new purchases or free weekend players are stuck until they fix it.
Third-party launchers on Steam are bad enough but third-party key generation is even worse. What a mess.
Update - 31/07/23: they did eventually fix the key issue, so I have been able to actually get in and confirm the game does indeed work now on Steam Deck.
You can play it free on Steam until August 3rd and it's also 80% off during this time.