Last I checked, the gog version is still missing a few updates the Steam version has. And those don't even address the broken pawn system which is supposedly fixed on Steam.

Added:
Guacamelee! Gold Edition
Hand of Fate
Risk of Rain
Slime Rancher
Stories Untold
The Lion's Song

Do you have a source for that statement by the Not Tonight developers?

Thanks! I think anyone can read it on the developer Discord, but as far as I know it isn't possible to provide direct links.

If you could take a screenshot that might help, otherwise there is a way to directly link to posts on Discord but you need to have developer mode enabled and that's just too much of a hassle. x)

Here is a screenshot

Thank you, do you mind if that's added to the spreadsheet as a source?

Sure, go ahead.

Anna's Quest doesn't have polish language on GOG but polish subtitles are available on Steam.

Thank you kindly.

Not Tonight added.
Anna's Quest added.

I've decided that the Land of Linux is a Swamp of Confusion.

STASIS added. (There is currently a beta Linux build available for Steam users but apparently GOG QA is scary)

A couple of games have been removed from the spreadsheet because they do not have Linux ports readily available anywhere. That includes Loki ports, for one, but also games that previously had ports which are now no longer available.
Missing ports made by Linux Game Publishing have also been removed as their entire site is currently not available, but can be added back later.

Removed:
Anodyne
Banner Saga, The
Book of Unwritten Tales, The
Cat Lady, The
Chaos Engine, The
Creatures Exodus
Cultures: Northland
Descent 3
Descent: Underground
Earth 2140 Trilogy
Evoland
Heroes of Heroes of Might and Magic® 3: Complete
Jack Keane
Jagged Alliance
Jagged Alliance 2
Knights and Merchants: The Peasants Rebellion
Lone Survivor: The Director's Cut
Majesty Gold HD
Quake III: Gold
Rune Gold (original version)
Sacred Gold
Samaritan Paradox, The
Seven Kingdoms: Ancient Adversaries
Sid Meier's Alpha Centauri™ Planetary Pack
SimCity™ 3000 Unlimited
SiN Gold
Sokobond (which had already been removed from GOG).


(Also changed a lot of unconfirmed "Missing Linux port"s to confirmed due to confirmation.)

Steam has a bundle of Jagged Alliance 1 + Deadly Games knows as Gold Edition and it shows Linux as one of the supported OSes (likely the DOS version running in DOSBox).

I strongly disagree. Contacting devs is the fastest way to change things and often it also helps GOG to get the actual update. Also the contact information is not at all classified so it's also not a secret. I would not post internal e-mail adresses but contact adresses that are available on the official sites of the publishers are the usual way to tell them what's wrong. IN several cases the devs/publishers aren't even aware that their versions are outdated. Many times I had success in contacting the publishers responsible and I will not change this. I will also not change telling others how to get in contact with devs.

You doing things your way isn't the same as having a public list with, these devs are bad, here's their contact info.

I also opened a support ticket about this and this is the reply I got from Virgile from GOG support:

"We will definitely have them. There's no ETA about it, and if needed, I can definitely refund you both games. Feel free to buy them again after, when the classics will be available. =)"

That still is no guarantee but sounds much more like "will be added" than your reply does.
But this is not what the list is about. The list is saying that those games are outdated, here's the contact for the people who can change this. As I said the adresses are not classified anyways so if I would want to just rant and/or even harrass them it would be easy to do so without any list anyway.

"I can only assure you that we're doing everything possible to get our hands on the best content possible. Unfortunately the process can be very complicated. There are many variables to take into account when trying to secure distribution rights from a publisher or developer, and it's not always possible to come to a compromise that satisfies all. This is especially true for GOG, as we want to uphold our core values (like no copy protection, or fair pricing), which do not always fit well into how the industry generally works. It gets even more complex with old content, especially games, whose rights are often in a state of “legal limbo”."

This is nothing but a PR canned response... I got the exact same message when inquiring about Kindred Spirits On The Roof Full Chorus DLC... doesn't mean squat.