After being in Beta for a while for pre-orders, Big Ambitions, a role-playing business sim from Hovgaard Games (who previously developed Startup Company) launched in Early Access on Steam and then dropped Native Linux support.
It entered Early Access on March 10th, with an announcement made in their Steam forum noting they "no longer offer native Linux support for Big Ambitions" but they will "continue supporting and testing against Proton" and they plan to get Steam Deck Verified too.
For players who don't see Proton as an option, they said Steam will give refunds.
As for why? They saw a "very high amount of non-gameplay-related bugs (random crashing, high VRAM usage, file access issues, etc.)" and noted the low amount of players on Linux so they didn't think it was "fair to the rest of our player base" to spend more time on it.

Direct Link
It's a shame when this happens but thanks to the Steam Play Proton translation layer, it does still mean Linux players will be able to run it and in this case the developer will support it there. Unless developers have Linux expertise and extra time for the currently smaller amount of users, Proton can often just work better, because it's constantly upgraded and optimized by Valve developers.
They're not the first by a long stretch to do this, and they won't be the last.
For one thing, I find that often developers who do have native linux support don't know what they're doing. For example, I've recently been playing the fun and relaxing board-game-like "Terraformers". It has native linux support, but they put their game data directly in `$HOME`, which is, of course, infuriating. I have posted in steam forums requesting they fix it, and it seems the developers do not even know about XDG directories.
Another (yes, very frustrating) thing to consider is that, while I assume most of us on this forum probably consider linux to be the only sensible operating system for software development, this is true of just about everything except games. If a developer has any intention to sell their games, they have to support windows, I'm sure there are even reasonable arguments that it would be crazy of a game developer to have a primary development environment other than windows. As a maintainer of open source projects, sometimes people complain to me about windows-specific issues, and my response is basically "good luck with that". It's hard to blame windows developers for taking the same approach.
Modern wine/proton works so well that I don't think it's such a bad thing that we lean heavily on it. My main worry is that I fear proton development is now irrevocably tied to the commercial success of the steamdeck, which is definitely not a great situation.
Native code on Linux should be what devs strive for. However with the substantial growth from Proton and the Steam Deck. We have options now that allow us to just leave that Windows build turned off. I literally only run Windows to play certain early access, and closed beta/open beta titles like Diablo 4(which works well on the Steam Deck too). I never saw this coming in my lifetime. We can all officially say we're Linux gamers, and not have people laugh thinking we can't play the latest titles anymore. We can build a PC now just for Linux, and not even think about installing Windows 11 telemetry edition.
Quoting: InhaleOblivionAnyone of us who has used Linux for years prior to the advances of gaming understands why those of us who are lifelong gamers have two PC builds.I am biased but I must say that 2 PCs sound overkill to me, compared to dual booting.
Quoting: InhaleOblivionthose of us who are lifelong gamers have two PC builds.Thinking back of the days we played Pong and Pacman.... Yepp I can consider myself a lifelong gamer.
But I do not know a single Person who maintains two dedicated PC hardware sets, one exclusively for Windows and one exclusively for Linux. (Assuming that Raspberry Pis and DIY servers don't count).
Dual boot
Quoting: TermyNot great - but as the explicitly said they will make sure it is tested on proton, i'm halfway fine with that.
Exactly halfway for me: explicitly having Proton as a development and testing target means that I'd get a game at 50% off, rather than at full price if they'd had Linux as a development and testing target.
Quoting: InhaleOblivionAnyone of us who has used Linux for years prior to the advances of gaming understands why those of us who are lifelong gamers have two PC builds.Nope. Gaming every single day for ~35 years, using Linux for ~20 years. If a game doesn't work on Linux, I'm not interested in it.
Quoting: mr-victoryQuoting: InhaleOblivionAnyone of us who has used Linux for years prior to the advances of gaming understands why those of us who are lifelong gamers have two PC builds.I am biased but I must say that 2 PCs sound overkill to me, compared to dual booting.
I don't know this game, but it's a terrible news.
I have 3 computers with the different Linux distributions to play different games published between 1996 - 2004 (e.g. Mohaa), 2004 - 2015 (e.g. Jack Keane), 2015 - 2023.
Quoting: CatKillerIf a game doesn't work on Linux, I'm not interested in it.And I still dual boot in 2023

One day, one day...
See more from me