Whether or not it's DRM comes down to intention, and I'm not a mind reader. If they're intentionally trying to create ambiguity between single-player and online functionality, something is wrong.

The primary issue seems to be not the quicksilver missions, but the quicksilver shop. As I understand it, you can get quicksilver offline (although it's much easier to do so online), but the quicksilver shop is almost empty. However, if you go online once, do nothing, and then return to offline, the quicksilver shop is suddenly populated with many more items, which you can buy with whatever little quicksilver you collected offline.

I don't use the term "DRM" because it's meaningless, since everyone defines it differently. But this does sound to me to be "single player content locked behind an online-only wall".

Disclaimer: I don't own the game, so my understanding is based on what others have posted here.

So you're saying you went online to get an update which you could then use offline. That does not sound like an online only paywall. It sounds like an online update.

if you go online once and then log off
and then items suddenly appears in the offline shop
it sounds to me like the game then fetch those items from the online server.
That doesnt really sound like DRM to me
That sounds like a supply mechanic.

Theres no reason the shop shoud be itemless in singleplayer content unless theres some sort of supply mechanic.
Recettear: An Item Shop's Tale comes to mind
In that game you had to farm items and materials to keep the shop filled

It migth be that the shop has to be filled by others online (Other players filling up the shop by selling farmed stuff to NPC or delivering quest items)
Alternativly you coud try to grind/farm stuff around offline and sell it to vendors that makes the supply chain complete in the offline content to fill the store up again or something like that.
Havent played the game myself
But it sure sounds like a supplymechanic system to me.

See above - there is no supply mechanic, it's just a simple check.
No, the only thing that changes is one value in the savegame.

If its just the savegame
what stops me from modifying my save file?

Have the game devs banned or barred me to make changes to the save file?

Nothing stops you from doing that. The file is plain JSON. You can edit it by hand (though valid values change with updates) and there are save game editors around too.

In fact, many long time players do just that, because earning the required quicksilver for the Living Ship mission can get boring, regardless if you do community missions or harvest the rare stuff in single-player.

And people who play completely offline do it to unlock the "Quincy" store. The point is, that this shouldn't be necessary.

Then the game do not contain DRM

to make comparrision
Toyata is gonna sell me a car
they have promised me that the car can go faster than 180 km/h
they havent told me how
and they just deliver me a car that can go 180 km/h
The argument here presented are the following
Its completly impossible to mod the car(change motor in the car in to a more powerfull one to make it go faster)
or if its possible, the ways to do it is surley not endorsed or in any way of form or shape supported or wery hard to pull off.
Later down the road as tech advances the factory or store one bougth the car from have made an even more powerfull engine.
Now, i can either mod the engine itself or buy me a new more modern engine
This requires permission or support from the manufacturer or unofficial support in any way form or shape.

Now heres the problem i see with the argument presented in this thread
Since the store is not delivering the new invented engine to me or is modding my old engine for free
then the claim is its bassicly impossible to mod the car and Toyata has broken their promise that the car coud go faster than 180 KM/h and they must have put a lock on the car preventing me from doing any modification myself despite not mentoining annywhere what that earlyer promise excatly entails into.

If there has been true DRM
then it woud be very hard to mod the the file
the dev woud surly not have supported it
and they woud have made evry effort to stop people from making such modifications to the game

The PC version of No Man's Sky can be modded to change features, and add in game assets.

Ps. Im Not saying mods are officially supported from the no mans sky team
but they surley as hell not banned it either
making the claim of drm a strange one, at least in this case.

Now, if hello games
had started to combat modding and make efforts into try stopping it
so that later down the road when the devs do not wish to add any more updates to the online version
making it impossible or very hard to modify the save file with the recent changes
then by all means its DRM content.

I think people in this thread are confusing inconvenienence with DRM
they are not the same

That depends on your definition of DRM, which is one of the main contention points on this thread. IMHO we should just agree to disagree here - some people think this kind of mechanic is perfectly fine, while others see it as a major offense.

The way you are defending it however, is by saying that "No true DRM would ever use something as simple as an online check/activation. True DRM is only something you really can't circumvent."

I guess I'll say it again, probably one final time: the main concern that has us "all fussed up like idiots" is the possibility that these kind of practices become common on GOG. Not just with NMS, but other games that may increasingly separate content behind a needless multiplayer/online wall. The keyword here being "needless". It's just not the direction some of us want to see GOG head into, and you may disagree of course, but that doesn't make it an invalid opinion much like your opinion is no less valid, though it personally saddens me to see more and more people who don't really mind this kind of behavior on the part of game developers.

It can. I've always played it offline.

It's a fair point and of course you are correct, that you can't please all the people all of the time. But, in my view, there is a very big difference between 'post-release support' and continuing to push substantial content changes post-release, to the extent that it even breaks compatibility with saved games and players have to literally start over. It seems to be a rather extreme case of 'post-release support'.

"We'll change the game on the fly however we feel like it and sometimes break your saved games" is pretty much at the opposite end of the scale to 'drop it and run'.

Yes this is true, however you are locked out of content if staying offline (which is how i play also, no galaxy, just offline installers and no internet connection).

We have a number of threads in the NMS forum that detail exactly what has changed in how NMS works in relation to needing to be online or not:

https://www.gog.com/forum/no_mans_sky/no_quicksilver_items_for_offline_players/page1

https://www.gog.com/forum/no_mans_sky/melody_of_the_egg_no_gog_galaxy/page1

https://www.gog.com/forum/no_mans_sky/company_unwated/page1

It's a problem, but one of Hello Games making (that they could fix quite easily).

I don't know if anybody thinks this is "perfectly fine".

If it's supposed to be some form of DRM, it's broken (and why put DRM some free bonus content in the first place?).
If it's supposed to be DRM-free single player content, it's of course also broken.
If it's supposed to be pure MP reward, it's also broken, since you don't have to do actual MP. It also begs the question why to lock a rather long pure SP mission behind some MP requirement, when alle the other reward items are only useless decorative/collectibles and the announcement of the Living Ship update never mentions that MP is required to get it.

The only reasonable explanation I can come up with is - it's some kind of bug/oversight, and HG deems it low priority compared to all the players with corrupted saves (which can mean a loss of hundreds of hours of play time).
That's not the case, except through bugs (which were, admittedly, not uncommon).
What players lost sometimes was the effort of building (as in: erecting) their bases, but they got the resources back for those (and farming resources is one of the main time-sinks of the game), so they could rebuild immediately, and they kept their ships and weapons - upgrading those is another major and time-consuming factor of progress.

Many players chose to start over anyway after major updates anyway, simply because it's fun. People with problems in their save games could send in the file and HG would fix both - the game and the file, and send the latter back.

The difficulty of breaking a DRM system does not equate to it not existing in the first place. Every edit not made possible in-game or using game-provided tools is in fact breaking the game. The savegames in NMS were never intended to be fiddled with, but the devs didn't bother trying to prevent it. And it's early days yet: the devs could rewrite the save system at any time making editing less convenient.