Firaxis Games recently launched their new Leader Pass for Sid Meier's Civilization VI, and it seems they broke it on both macOS and Linux.
The Linux and macOS versions were done by Aspyr Media, who don't really do ports any more. The store page on Steam still shows both as clearly supported though, and the new Leader Pass indicates both are supported platforms too. However, the macOS and Linux support topics on Steam are filling up with people reporting the game is now broken or has major issues on these platforms.
For the Linux version, it seems the update actually downgraded the game to a much older version "184.108.40.206" (I was able to use an old workaround - see the bottom, to get it to launch) with the latest being 220.127.116.11. Even for people on macOS who have managed workarounds, some are reporting other major problems like Civ Vi eating all their RAM.
At least for Linux users, a workaround is to use Proton on it to run the Windows version. Here though, some users report the 2K Launcher doesn't work, but for me it was fine. You can skip the 2K Launcher on Linux with Proton by adding this as a launch argument for the game on Steam:
eval $( echo "%command%" | sed "s/2KLauncher\/LauncherPatcher.exe'.*/Base\/Binaries\/Win64Steam\/CivilizationVI.exe'/" )
It's a shame, as it shows even though they're selling it clearly as supported, seemingly no one at Firaxis / 2K / Aspyr is even testing either Linux or macOS now.
I've reached out to the publisher to see if they have anything to say about what is happening, although they never replied to my initial email asking about the new DLC. I've also reached out to Aspyr Meda directly about it. Will update if either reply.