It's been a long time coming and the wait should hopefully be over soon, as Aspyr Media have confirmed the next Linux patch for Civilization VI is waiting for approval.
Back on July 20th, when we last spoke to Aspyr they confirmed to us that they were hoping to have it up in the next few weeks. Thankfully, it seems they're going to hit it! Only yesterday, they said this on the Steam forum:
We have a final candidate we are happy with, and we are hopeful for partner approval soon.
They also clarified in a later post, that this patch will actually include online cross-platform play for Linux, Mac and Windows! They've had a lot of problems trying to get here, as they've posted about before so I'm sure many of you will be happy to see the day finally come.
We know it's not always a simple job to get cross-platform multiplayer for Linux ports, as they're not the only ones to have trouble with it. Feral Interactive have also talked about this numerous times with their ports, so it's not something specific with Aspyr Media. I imagine it wasn't just a case of getting the code in place, but likely convincing the original developer/publisher of the Windows version to adjust things on their end too. So with that in mind, I do appreciate the effort—I just wish it happened sooner.
Hat tip to SadL.