Ubuntu 18.04.2 LTS on AMD64 with Steam client now at version Feb 18 2019, package 1550534751.

Yesterday, I could play Steam Play games (Windows games with the Proton fork of Wine) just fine on my machine. I rebooted, and Steam updated itself, and now none of those games run. When I try to start a game, I get errors like:

run-detectors: unable to find an interpreter for /home/jwatte/.local/share/Steam/legacycompat/iscriptevaluator.exe
run-detectors: unable to find an interpreter for /opt/steam/steamapps/common/ForgedBattalion/ClientLauncherG.exe

(I also get a few assert failures in AssertMsgImplementation(), which the Internet seems to think are red herrings. Asserts in shipping code are of course bad, but as I don't have the source, what can I do but trust this?)

Additional searching says that this is because the binfmt database doesn't contain Windows PE32 files, and true enough, update-binfmts --display does not show any binfmt that uses wine/proton.

Before I go ahead and try to patch this myself with update-binfmts --install and trial-and-error, is there a ready-made file to import for proton? Or is it supposed to work some other way, and something's broken on my system? I'd rather stay as close to vendor-supplied installations as possible, and not add too much customization myself...


So, it turns out this is a bug in the current Steam proton download code. It's "available" but doesn't get downloaded when selected. The work-around is to select to install some new Windows game (that isn't already installed) and it will also install the new version of Proton.

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