AFAIK, Unity-the-engine still has a vsync bug
edit: on Linux that makes running unity games on my laptop burn one of my CPUs at 100% nonstop. It heats the thing up, burns precious battery life, and is doubly infuriating if you're playing a game that should be light on resources, like TIS-100.
This has been an issue for years, and they can't be bothered to fix it.
edit: the reason is obviously that Linux is a small customer base, and you'd only notice this on Linux laptops, which is an even smaller subset. However, for indy developers in niche genres (where in some cases, like TIS-100 for example, you can expect a more significant chunk of Linux users), I think the fact that Linux support supposedly comes for free is one of the reasons to use Unity, making this doubly cynical.