I don't own all games to test and rely on contributors both here and on PCGamingWiki. Personally though, when I test a game I do what I described in the original post ("Ideally if you have 2 or more PC's, the games could be downloaded on one and tested on another (preferably offline) to rule out any potential Epic Store equivalent of Steam's CEG (locking games to specific motherboards)"). This also detects things like missing registry entries (rare on modern games but it does occur on older ones even here on GOG, though it's more an issue for older 90s titles that Epic doesn't tend to sell).

I also run a WhiteList Firewall (Block by default, Allow by Exception) instead of the default Blacklist Firewall (Allow by Default, Block by Exception). This blocks Internet connections which as you correctly said, that can flag errors. Not everyone does this here, however I'm also an editor at PCGW and am aware that some over there who do test Epic version DRM do make sure to disconnect from the Internet. Sometimes there may be a sign of Internet Required in-game, eg, The Talos Principle throws up an in-game login screen not seen on the GOG version. Generally though if an Epic Store game does require Internet Access, it does it through the client and if that isn't running it usually just won't start in the same way DRM'd Steam games don't. You are correct though that where possible, testing with Internet temporarily disabled is a more thorough test against unwelcome "surprises".

I've tested Airborne Kingdom on a separate computer with internet disabled and it still works, so that entry remains valid.

There is something to be said for invested time. Most updates are community work so in my opinion every bit of info should be appreciated. Turning off the client or adding a switch is reasonably easy to do. Interchanging save games and testing DLC can be a long and laborious job. I for one always game on my only proper PC and I am not going to switch off my internet whenever I want to play a game. I test the games I buy because I want to know if they can still be played if the EGS disappears, not because I actually want to play them without the client now. In the end whoever really really wants to know should buy and test the game themselves.

Alien: Isolation runs with the -EpicPortal trick, but you can't save your game unless you're logged into the Epic launcher.

This is pure evil, SEGA is irredeemable.

Can modders find a way to fix this so the game can save when not using Epic Launcher?

Is it like Journey then? I recently did a lot of monitoring of the game behavior and discovered that the reason it now requires the launcher to save progress is that it uses the platform-agnostic Player Data Storage feature of Epic Online Services, storing all saves in the cloud and leaving a copy in %LOCALAPPDATA%\Temp\datastorage\ but never reading from it.

I assume it still works offline on Steam after activation or else we would have heard about it, so it just needs the client itself for random checks like this? That's... weird.

Thanks for the confirmation guys. Given that I've no choice but to add it to the DRM'd tab.

Roze explained it better but some games like this seem hard-wired to both want to save to the cloud by default and to expect the client to handle that. No client = no save. Aside from Journey here, some Steam games on this list are like that, eg, Cognition: An Erica Reed Thriller, Dammerlicht, Death Goat, Detention, Ittle Dew, etc, and as far as I know it hasn't been solved through modding (obviously cracking the DRM out of game / using a client "emulator" may work but that's not really what this list is about).

Assuming you mean "offline mode" as in running the game with the client running (vs client-less and actual DRM-Free), it's entirely possible that the Steam client may work in the same way but the client contains "fallback code" that caches a "cloud save" to a local folder whilst in offline mode whilst sending a "success" flag to the game after "saving to the cloud". Kind of like how galaxy.dll files do for GOG offline installers act like a failsafe so that a client-less GOG game doesn't crash when flagging an achievement via a dll call to the not-running Galaxy or something similar.

Yeah, probably. I just find it interesting that even a game with the DRM'd client requirement after install would need the client after launching it in offline mode, but what you say makes sense.

Anyone plan on picking up Super Meat Boy Forever today? I'm dying to know whether or not that one's DRM-free, like the original one is.

EDIT: I can confirm that the game is completely DRM-free, and it saves outside of the client, to boot.

Does World War Z's DLC's from GOTY Edition work when not running WWZ with Epic Launcher in the background?

It doesn't, only the base game works.

Sweet. Going to be getting that with the coupon.

Btw does anyone know if Going Under is DRM Free?

The two latest free games, Metro 2033 Redux and Tropico 5 can be played without epic and without an internet connection. Tested on Win 10. Savegames work for both.

Do note that I don't have any Tropico 5 DLC so I was not able to test that.