For achievs you'll need to check the spreadsheet in this thread:
https://www.gog.com/forum/general/list_of_broken_gog_achievements/page1

For the other issue.. I don't know.

Have any GOG employees ever responded to these concerns?

So, the DLC for the Quest are done by a separate person to the main quest game, this is why it’s an issue on pc, yet they are sold normally on iOS and Android. Now this one person says they do not want to have to collect money from and post updates to various sites. They are only happy posting updates to steam workshop and collecting money from there. And yes, steam workshop does host paid content.

The upshot is that the only way to obtain the dlc for the quest, is to do so via steam and pay and download them from workshop, and that is how it will remain.

This is what Steam has done for PC gaming!
Nope, it’s very unlikely they would or even could.

This is more for people considering whether or not to buy a title. Check the list and see what's missing or if the game is no longer supported.

I don't see Neverwinter Nights Enhanced Edition on the list yet, but I think it fits, too, at least partially.

- Partially because GOG is the only one still giving away Neverwinter Nights Diamond with each purchase, and in that regard GOG customers are actually privileged over those of other stores.


But in all other aspects, if you disregard DRM, GOG users get the short end of the stick:

- The Enhanced Edition frequently gets development builds with fixes and new features on Steam, while GOG does not support them. GOG only gets the official patches, and because of that it took one whole year for all the little fixes and features to finally arrive on GOG last year, while Steam users received constant updates.

- GOG users also had to wait for the new Premium Module DLC Tyrants of the Moonsea, which was released here one month later than on Steam, without any conceivable reason and without Beamdog or GOG giving any explanation for the disparity.

- The latest official patch was released on Steam on Tuesday, and Beamdog said it should arrive on GOG the same day. The next day it was released on Galaxy apparently, but so far, the offline installers are still outdated. Galaxy is not the same as GOG, so for all GOG customers who don't use it there's an unknown delay and no communication about it, once again.

In short, I'd say if you want to play NWN Diamond, GOG is the place to buy it, if you want to play NWN EE, Steam customers are much better off than those who buy it on GOG.

Dark Quest 2:

Playing custom maps requires Steam Workshop, so this function does not work in the GOG version. Apparently you can see the button for it in-game, but if you click on it, it just says "You havent downloaded any maps yet", and for that you'd need Steam.

Ultimate Doom and Doom II + Final Doom

Both games received a new Unity-based version (see link below for more info), exclusively on Bethesda.net, some months ago. This wouldn't be so bad if the original versions weren't included, but they are. So, at the cost of 5 bucks for each game, you get access to both the original DOS and the new Unity versions. In addition, Final Doom is available as a free add-on for either game and No Rest for the Living (previously, a Doom 3 BFG-exclusive on PC) is available as a free add-on for Doom 2.

https://bethesda.net/community/topic/369943/doom-doom-ii-patch-notes?language%5B0%5D%5B%5D=en

If you want to add all GOG games that may receive updates a bit later and less frequently than Steam versions, then I guess you could just as well list all new-ish games that still receive updates.

I have simply come to accept that, I am not even requiring that an update necessarily needs to come to GOG, and especially the offline installers, at the exact moment that it appears to Steam. In fact, I would probably just get annoyed if the offline installers were receiving daily updates. People who want updates that often SHOULD use Galaxy, due to auto-update.

Point taken, but only in part. I'd say waiting one year for bug fixes is more than "a bit later and less frequently than Steam versions", and Galaxy users don't get updates for NWN EE more often than offline users either. And "daily updates" is a huge exaggeration, Steam users get one maybe every 1-3 months or so, and NWN EE could actually be compared to an Early Access project, as far as the "Enhanced" is concerned.

Niffleheim is still at version 1.0.10.1, while steam is on 1.0.11 since 2nd march. It's mostly chinese version (apparently pretty bad) but also some bugfixes.

I will take care of this. I am still in contact with them because of the missing DLC and they said it's difficult (for whatever reason). I am really curious what the explanation for the missing update will be ;)

I contacted Niffleheim devs about it and the response was that traditional chinese translation is the only difference between what we have here on GOG and Steam version. But the Steam news article mentions bugfixes, so I asked them about those today. They also said that DLC they are working on now will also be released on GOG.
Edit: According to devs the fixes from 1.0.11 steam version are also present in GOG version. So it seems the only difference is the lack of traditional chinese.

That is exactly what they told me. They also told me that GOG will receive the update as well (see attachment).