PC.
The error message only happens in offline mode. In online mode it's just the launch loading bar that hangs indefinitely. I can repair and uninstall/reinstall games okay.
And in fact after finally finding a way through the official help pages to try and report the bug I found the live chat, and I was advised to uninstall both game & EA App and restart PC using clean boot and reinstall both. I tried that and currently some games seem to load in offline mode (whether or not that will remain true I'm not sure), but the one I did the full re-install of still gives the EC:204 error in offline mode or hangs in online.
...Or did when I tested it after doing the re-installs. Now, when I test it to confirm the error code, it runs fine and I'm really confused because literally nothing has changed since the last time I tried to run the game offline and now.