For Civilization VI the final huge update (April 2021) has been released for Linux:

We’re excited to announce the April 2021 Game Update is now available to all Civilization VI players.

In this final free update of the season comes new units, new maps, and several balance adjustments and gameplay fixes based on player feedback. Read on for the full list of what’s available in today’s free game update.

BUY THE NEW FRONTIER PASS

[NEW FEATURES]

New Units

An free update for the Euro Truck Simulator 2 now adds the new Renault Trucks T & T High: Evolution!

The full announcement can be found here.

An experimental cross-plattform-multiplayer for the theme-park-management-game Parkitect adds the possibility, to play the multiplayer with other platforms than Linux:

Experimental cross-platform multiplayer available

An experimental update for cross-platform multiplayer is now available for testing.
This allows all players to play together, no matter if you're using Windows, macOS or Linux.

Another huge update (v.13) called "Esparcidor de Estiércol" for Tropico 6 has been released for Linux on Steam:

Update (v.13) 'Esparcidor de Estiércol'

Fellow Tropicans,

Tropico 6 has just received Update 13 – Esparcidor de Estiércol. This update introduces the new ‘Flophouse’ building - providing, well... a roof (at least) for the poor - and the ‘Manure Spreader’, which should help put all that llama poo to good use.

For the free Raytracing-enabled version of the classic shooter Quake 2 the Patch 1.5 has been released for Linux on Steam:

Quake II RTX 1.5 PATCH

Hey, everyone! Today we're releasing v1.5, featuring the below features, fixed issues, and improvements.

New Features:

The Update 32 for the racing simulation Revhead has been released for Linux on Steam.

Date: 26-03-2021
Version: 1.4.7853

Dear Revheads

It is our Birthday Special Days, as you might know, Revhead turned to 4 years old. While our discount is still on for another week long, we are releasing new content as well. This is one of the best time of the year to grab your copy of Revhead!

The very huge Updates 1.40 for Euro Truck Simulator 2 and American Truck Simulator are now available for Linux on Steam.

The complete list of all changes (for ATS/for ETS2) is large, and include a completly new lighting system for the underlying engine and also revamped trucks and cities.