Some of those might not be the fault of paradox, but Imperator shows that they didn't even test running it on a stock install.
I've had better luck with proton games, they don't always work but once they do I have far less regressions.
Granted, I'm on Slackware64-current, so it's possible I've got newer driver/lib versions than Ubuntu 18.04. I'm also using FOSS drivers exclusively (primarily AMD, though I've played Stellaris on Intel GPUs with decent results, too), so if you're using Nvidia graphics, that might be a factor, too.
Not sure what you meant, but X.Org is an implementaion of X11 so this doesn't make any sense.
Currently on wayland stellaris and EU4 won't start for me, I didn't even know stellaris was broken until now, that was one of the better working ones.
On xorg they will all start but games are offset and sit below the top bar in gnome, The mouse isn't offset so it's completely unplayable. One of them used to work fine in xorg though, not sure which.
It's also been a while but I wasn't able to play CKII or EUIV against friends on Windows due to some clock-time issue. Not sure if that's still a thing, but it led me to use CKII in WINE while doing large multiplayer games.
edit: otherwise, single-player native linux has been solid with CKII, HOI4, and EUIV, including mods. Vicky II did fine in WINE. I'm running new-ish Fedora.
Nov 2018 - Artifact (Collectible card game on Windows/Linux/MacOS)
Apr 2016 - The Lab (Windows only)
Dec 2014 - Left 4 Dead: Survivors (Arcade game?)
Oct 2014 - Counter-Strike Nexon: Zombies (Windows only)
2013 - Counter-Strike Online 2 (Windows only)
Heck even their new tentpole title Half-Life: Alyx is Windows only. Those aren't really big Linux credentials to boast about.
Half-Life Alyx is coming in 2020.
The meme that Valve doesn't make games isn't real.
Even to hold people over they could have resurrected HL:DM and made it F2P.
So sure, Alyx is coming. But before that is a six and a half year gap in major games.
And if you discount CS:GO and Dota 2 as remakes, then you're looking at Portal 2 all the way back in 2011.
I’m 100% not complaining because Proton has enabled me to play a libraries worth of games that were previously unavailable but it’s not exactly a victory Linux. The future might look like devs testing a little bit in Proton as “Linux support.”
While it is an admission Linux gaming was hardly going to take off on its own from a cold start, it allows people to use the platform that makes more sense for them. With the increased capability of Linux+Proton as a platform, its horizons are pushed and it makes more sense for more people.
The only possible downside here is the potential for a developer to neglect Linux support now that people "can just run it in proton", netting Linux users a couple losses of what-would-have-been native ports. However, I believe the increase to the viability of Linux gaming overall makes up for it.
All source games work on linux, but the new half life game might be the first exception. Proton works pretty well for other games, but there are hard blockers on some (for ex: the anticheat in pubg)
Is that due to active development effort or is it just chance?