Recently Sid Meier's Civilization VI from Firaxis Games had a major update and DLC release that broke it on macOS and reverted to a really old version for Linux but porter Aspyr Media has partially fixed it for Linux now.
For the Native Linux build, it is at least now up to date with version 126.96.36.199 instead of the really old version they seemingly put up by accident. It still won't launch on a lot of newer Linux distributions without workarounds though, which Aspyr are likely to never fix and that has been a problem for years. This means the new Leader Pass should work fine.
As an example of the Linux workaround for the Native version, you can use a simple Steam Launch Option:
I'm still honestly amazed such a seemingly simple library issue was left in for years. It's also surprising it took over a week for them to fix the wrong game version for Linux…
However, due to performance, you're likely far better off with the Windows version in Proton and you can work around the problematic 2K launcher with this Steam launch option:
eval $( echo "%command%" | sed "s/2KLauncher\/LauncherPatcher.exe'.*/Base\/Binaries\/Win64Steam\/CivilizationVI.exe'/" )
Seems like they haven't yet fixed it for macOS, with lots of complaints on Steam about it. Aspyr really dropped the ball on this update and the annoyance from users is quite understandable.