Terraria didn't get Steam multiplayer until the latest update; it was always just direct IP for years. A tiny game you probably haven't heard of called Minecraft has LAN/public servers. And so on. It's pretty disingenuous to claim that DRM-free multiplayer is extinct.

Not extinct, just highly endangered.

Is having to create a GOG account to buy and download games considered "DRM," considering you need to be online to do both?

No, despite a common misconception DRM have nothing to do with being online. A DRM is any digital restriction added to control the usage of a software you already bought. So it would include a mandatory login on game launch, or an imposed third party software to download the game or its updates.

Being online to play an Internet-based multiplayer game is nothing but a technical restriction, and could not be qualified as DRM. This is of course the same about the requirement to have an access to Internet to download a game installer.

On the other hand, a mandatory online connection to play a solo game, or the inability to host a multiplayer game without going through a central server, these are artificial restrictions that qualify as DRM.

I think singleplayer would have the bulk of the attention for DRM-free, and there are games (like FEAR) that have DRM in the multiplayer and it warns you not to use it. Then Neverwinter Nights has DRM where you need a unique CD key (which they provide you one)

Seems more annoyances than actual DRM. Other things just want you to log in to submit to leaderboards. ToME comes to mind.

Indeed. Though clever enough hackers can remove portions of the checks to make the games as DRM-free as possible. Though cheaters likely can totally screw the game up too.

Though there are plenty enough DRM-free multiplayer options. Maybe not the hottest or newest games, but there are enough out there.

Only to the extent it keeps anyone that hasn't bought the game not to download it DRM as it restricts access.

But Uniqueness is hardly a qualifier for DRM.

having to be online is not DRM in itself, it is what happens with the online session. Having to be online to play a game, is no more DRM then having to use Windows, or DX10 or indeed electricity.

DRM is (hopefully still) digital RIGHTS management, and if there is no management of your rights then it does not apply just because you have to be online. if it is then.... having to use electricity is DRM as well. it is not DRM, it is a dependency.

if the online session do check your rights play the game, then yes it is DRM, but being online is not DRM by default.

At least three games in the last couple of years have "no account based" multiplayer: Stardew Valley, Grim Dawn, Monster Prom. I think they all might use GOG on the back end, and two of the three have LAN play/direct connect in them.

Store page for Grim Dawn says "Please note that the GOG GALAXY Client is required to access Multiplayer." Are you able to play Grim Dawn multiplayer without a GOG account?

To my knowledge, an account isn't even needed to play Factorio multiplayer if you're hosting your own server. I have no idea what the OP is complaining about.