I recently found a GOGmix (via community wishlist) for games with local content locked behind DRM. I remember that some Topware titles requiring CD key and/or third-party account for LAN were listed. I have tried using a custom search on Google.
The list excluded multiplayer games and wasn't a catalogue of products with activation keys, and had over 700 votes if I remember correctly. Can you find what I'm looking for?

For a custom search, you can use a subdirectory in your site: bit.

Like this: https://www.google.com/search?q=site%3Agog.com%2Fmix+multiplayer

Is this what you;re looking for? https://www.gog.com/mix/games_with_multiplayer_drm

Thank you for Google search advice, but as I said the list wasn't about multiplayer games.

Sorry

Search with the "display just a few of the URLs" filter off:

https://www.google.com/search?q=site:gog.com/mix+singleplayer+drm&filter=0&biw=1920&bih=986

I see this: https://www.gog.com/mix/good_old_games_with_bad_ol_drm

I point it out since the Age of Wonders 3 review specially mentions needing an account to play the game, even with single player.

Although the list only has 2 games listed.

You don't need an account for single player, you have access to all the offline features in Guest mode you only need to create a Triumph for multi player.

EDIT: I read your review and never did it mention that you need to have an online account for single player.