[2020] no more offline play?!?!?!?

No idea how you did that, but Eco never supported offline play, including not in 8.x.

I can't tell you much more than Eco has never supported offline play and questions like this have sprung up before - so it was affecting people before. I'm sorry that it was working for you for some reason before and now is no longer, but it wasn't intended to work. (The same goes for family sharing)

We have no plans for an offline mode for Eco, sorry.

Single player has nothing to do with DRM. The game has singleplayer, no reason to remove the tag.

Not sure who told you the above. As i said, it was never supported. If it worked, it was a bug.

The menu doesn't vanish when being offline (but maybe I misunderstand you?), you just can't login / start a game / join a game as all of these actions check the license. (E.g. opening a singleplayer server does so as well, singleplayer is simply a server locally) Whatever you experience, it is a different issue.

For the other posts: As i stated before singleplayer has nothing to do with DRM, there is a lot of singleplayer games that require you to login online. I get that you don't like that, I do neither personally, but it's company decision to have it this way. Both sides have reasonable arguments.