The Chinese version of Wonderland Nights: White Rabbit's Diary, 仙境之夜：白兔奇幻记, can be played without Steam right off the bat. No special preparations needed. I didn't test the version under the appid 1238710 yet.

Store link: https://store.steampowered.com/app/1408540/

The game is only supported on Windows, according to SteamDB, but it also comes with a Linux executable in the installation folder (as usual for Ren'Py games), which also works without Steam.

I tested the Windows executable (WhiteRabbitsDiary.exe) in a Windows 10 virtual machine, and the Linux executable (WhiteRabbitsDiary.sh) in both my main Ubuntu install, which has Steam installed, and an Ubuntu virtual machine, which never had Steam installed.

About the Linux executable, when launched from the command terminal, it always complains in the log that it failed to load the Steam API, whether Steam is installed or not, or if Steam is running or not, and Steam never seems to detect the Linux executable as running. But from the short tests I did in both Ubuntu installs, nothing seems to break because of failing to load the API.

And lastly, just a tip: the game's default language is Chinese, but it can be changed to English. For that, go to 设置 ("settings", in Chinese; pointed in the attached image "step 1.png") and click in the option 英语 ("English", in Chinese; pointed in the image "step 2.png"). And sorry for the image quality, but I had to downscale a lot because of the forum's 500KB limit.

Primal Light and Garlic work without the client. No special tricks required. Just play straight from the .exe.

Tested on Windows 7.

Primal Light

https://store.steampowered.com/app/771420/Primal_Light/

Garlic

https://store.steampowered.com/app/1250440/Garlic/

Windows 11 has been announced this past week, and with it, its requirements.
Among those requirements was mandatory TPM that needs to be on at all times.
From what I read, TPM acts as a type of DRM that ties a piece of software to your current hardware.
If Steam games start using TPM as a form of validation, would it mean that even if you use dual boot with either Linux or Windows, or even virtual machines, games with such DRM would still be able to check your hardware to validate the games?

Hardware based validation DRM already exists on Steam: it's called CEG.
Windows (OEM) activation has been tied to computer hardware for YEARS.

Like you can see on PCGamingWiki does Scarlet Nexus run without Steam by adding the steam_appid.txt
Additional Informations from my test yesterday. You then need to open the exe in <path-to-game>\ScarletNexus\Binaries\Win64\ and not the one in the direct gamefolder. The PreOrder DLC does not work DRM Free and the SaveGame location is moved to the configuration folder. From %LOCALAPPDATA%\BANDAI NAMCO Entertainment\SCARLET NEXUS\Saved\SaveGame to %LOCALAPPDATA%\ScarletNexus\Saved\SaveGame
Edit: Tested Version is 1.0.2

Holy moly. That is a big deal. Thanks for letting us know. Do you know if Code Vein is now drm-free?


Also, I've tested No More Heroes 1 and Monster Hunter World. Both still require Steam to run.

Code Vein still uses Denuvo. While the storepage doesn't have the usual notice, it is being mentioned in the EULA.

Thanks for letting me know. I really wish that these publishers were more honest (and upfront) about what is in their games.

Femboy Bangers: As usual for a Ren'Py game, it includes both Windows and Linux executables (FemboyBangers.exe and FemboyBangers.sh, respectively), and both work right off the bat, not requiring any special setting up.

Girls and Dungeons: Works right off the bat, no special setting up needed. Just didn't test it with the uncensor patch.

Girls &amp; Dungeons 2: Works right off the bat, no special setting up needed. Run either \Girls & Dungeons 2\Game.exe (on Windows) or \Girls & Dungeons 2\www\index.html (OS-agnostic, just need a browser that can run games from html files). Also didn't test the uncensor patch.

My Goddess of Love: Another Ren'Py game, and it also includes both Windows and Linux executables (MGoL.exe and MGoL.sh, respectively), and both work right off the bat, not requiring any special setting up.

Tamashii: I couldn't make the base game work on either Windows or Linux, and Wine even complains about requiring Steam to run the game, but if someone managed to make it run without Steam, please do mention how. On the other hand, the game also comes with a password protected file "Bonus.rar" that includes some prototype builds and a game that I'm not sure how related it is to Tamashii, and they all work without Steam, no special setting up required. You can get the password in-game, but [gameplay spoiler, I guess] if you don't want to play the game to find the password for Bonus.rar, the password is 586231571

True Hentai Puzzle:
- Linux build: Create a steam_appid.txt file in the game's root folder and place the game's appid (780020) inside, then run either First Day.x86 or First Day.x86_64, depending on your OS's architeture.
- Windows build: Same thing as the Linux build, but you need to run True Hentai Puzzle.exe instead.

Tested the Windows and Linux builds for each game whenever available. Only skipped the MacOS builds, as I don't own a Mac computer to test.

Femboy Bangers and My Goddess of Love tested in both a Win10 and Ubuntu 20.04 virtual machines that never had Steam installed.
Girls and Dungeons and Girls & Dungeons 2 tested in a Win10 virtual machine that never had Steam installed.
Tamashii and its bonus games/prototypes tested in a Win10 virtual machine that never had Steam installed and on my main Ubuntu install with Wine.
True Hentai Puzzle's Linux build tested in a Ubuntu 20.04 virtual machine that never had Steam installed.

And by Tamashii's log on Wine in my main Linux install (which has Steam), I guess it's safe to use Wine to test the presence of DRM, as Wine seemingly couldn't detect Steam's components from Linux (still not sure why I received such walls of text as replies last time I asked about it, when a few lines of logs would've been enough).

I see Gunman Clive is on the list as DRM Free. Well I just found that Gunman Clive 2 is as well.

Okay, we're all updated again!

Annalyn works out of the box without the Steam client.

https://store.steampowered.com/app/1508460/Annalynn/

Breakpoint requires the steam_appid.txt trick to play without the client.

https://store.steampowered.com/app/1273250/Breakpoint/

As always, Windows 7 for me.

Is it possible to include the testet version and testdate in the wikitable? So you can see that the game may have changed and is not DRM Free anymore?

That's interesting, specially since some tools, such as SteamDB's plugin, show the last time the game or app was updated.