Exophase shows the following games have achievements now:
Asterix & Obelix XXL Romastered
Hellpoint
Knightin’+
Moonlighter
Necrobarista
Yestermorrow
I don’t have access to a computer with Galaxy to test it now, so I cannot confirm which of these do have working Galaxy achievements.

Thank you SCPM, I have contacted basically all the developers of these games in the past, so I was keeping an eye on them and in fact I could finally remove some of them from the list.

Asterix & Obelix XXL Romastered - Judging by the percentages, the achievements seem to be operational, so I remove it from the list.
Hellpoint - Also this, judging by the percentages, the achievements seem to be operational, so I remove it from the list.
Knightin’+ - In this case the achievements were visible since the launch, but the developer specified in the game sub-forum that the engine that he used is currently not supported by the Galaxy API and hopes that things will change.
Moonlighter - When the achievements appeared a short time ago they weren't operational, so I contacted the developers, who told me to contact the 11 bit studios publisher, who told me it was a mistake, and then they removed the achievements to my great disappointment.
Necrobarista - The developers kept their promise and added them. Judging by the percentages, the achievements seem to be operational, so I remove it from the list.
Yestermorrow - Another welcome addition. Judging by the percentages, the achievements seem to be operational, so I remove it from the list.

Despite being advertised on the game card, Galaxy achievements for Super 3-D Noah's Ark are neither unlocking nor visible anywhere.
Edit: Nvm, the achievement for finishing level 2 unlocked, but not the achievement for finishing level 1.

Thank you, it seems to be yet another game affected by the annoying bug of invisible achievements. Either GOG explains better to developers how to make them visible, or they monitor this parameter more carefully when a game is launched, or even better they make the transition from "hidden" to "visible" achievement automatically when the game is released, because the situation is getting ridiculous.

Anyway, there is at least one achievement of this game bugged apparently, which guarantees him a place in the list.

And Infectonator 3 does have working Galaxy achievements, but I had to wipe all save files and data to get them to unlock, as though the game was installed on my computer for the first time.

Ooh, this is really interesting, there was no clue that it had them, neither on Exophase nor on GOG. The combination "invisible achievements" + "no tags on the game card" makes it virtually impossible to find out if a game has achievements unless you actually try it with Galaxy. Now I have quite a few things to report to GOG support.

Thanks again for the list. I had contacted the Necrobarista devs a while ago and did not get a response. Glad that they added.

Not sure if this is the right place to post, but any update on Ion Fury? I had tried to contact 3DR but could never get in touch with anyone. Not sure what they seem to have against GOG.

I contacted the developers of Necrobarista on Discord and they were always very kind and helpful.

The same can't be said about Ion Fury's developers. I and other people interested in the achievements have tried to contact them several times, and they have always completely ignored the questions, if not shown some hostility to GOG users. If I remember correctly one had also commented that the game sold well on GOG even without achievements and so it was useless to waste other resources on it. The game was also without updates for months on GOG.

The work ethic for some of these people is very difficult to wrap my head around. If I approached my work the same way that some of these game devs do, let's just say that I would be in a lot of permanent trouble.

Pathetic to see 3D Realms stoop so low, but given some of their issues through the years it isn't entirely surprising.

It is amazing how paradoxical things sound.

Some developers respond that it is not worth the time and resources spent to implement achievements at GOG because their game did not sell well, while others say that as the game sold well, it is unnecessary to add achievements.

The excuses are getting worse and more ridiculous!

NOTE: I also tried to contact Ion Fury's studio, e-mail and Discord, but they never responded.

Does Raiders! Forsaken Earth actually have achievements? I see no achievements listed in Galaxy, nor any ingame achievements list.

It's possible that it's the umpteenth case of game with working but invisible achievements, but to verify it you need someone to try to get an achievement and I don't know anyone who plays it, let me know if you find out something!

Hey, as for your list "Missing Galaxy Achievements" - according to Exophase, "Infectonator 3: Apocalypse" seem to have galaxy achievements implemented now:

https://www.exophase.com/game/infectonator-3-apocalypse-gog/achievements/

As i can´t find any Changelog so far & do not own the game:
Achievement support It´s not mentioned on Gog Gamecard.
So maybe somebody who owns the game can please kindly confirm?

I can confirm, take a look here:
https://www.gog.com/u/SCPM/game/1560654450

Hey there, cool. Thank you for confirming. :-)
So, one less entry on Alexim's list.
On Exophase they just mention 5 Gog trophies, but as you have the whole package of 41 (as on steam) - so i guess it´s up to Exophase to fix this. :-)
Thanks again.