The newest Update 1.4 for the Farming-Simulation Stardew Valley is utterly extensive and has been released just now on Steam.

Here is the "condensed" version of the Changelog (without spoilers);

Hi everyone,

Sigma Theory: Global Cold War, the "" leaves Early Access after seven month with a new update.

Sigma Theory is finally out of Early Access!
The 1.0 update is available to download from Steam now!
The current game has nothing in common with the one we've released 7 months ago. We've worked hard fixing bugs, improving feedbacks, adding content, fine-tuning mechanics and balancing gameplay with your feedback and support to come up with the best version of the game you get today!

GOG also has a Halloween Sale 2019.

It will last until 04.11.2019.

SteamWorld Quest: Hand of Gilgamech, the new card based RPG from the developers of SteamWorld Dig and SteamWorld Heist, is now also available DRM-free for Linux on GOG!

For the RPG Pathfinder: Kingmaker the so called "Enhanced Edition" has been released:

The EE includes:

For Stellaris the new (paid) DLC "Ancient Relics" has been released for Linux on GOG and Steam.

Also Stellaris is currently available for free on GOG Connect, and the huge Update 2.3 ("Wolfe") has been published!

A huge patch 1.6.0 and a new (paid) DLC "Urban Warfare" are now available for Linux on GOG and Steam!

Urban Warfare brings 'Mech combat to the vast cityscapes of the Inner Sphere! Electronic warfare, large-scale building destruction, environmental mechanics, new enemy units and more make the urban sprawl a whole new battlefield.