The listing, as spotted on Twitter by Klobrille, is for a Houdini Technical Artist to join the studio's world-building group - Houdini is an asset creation tool, in case you thought that Obsidian is specifically trying to recruit the long-dead escape artist. Among its list of "pluses" for potential candidates is "an understanding of the material editor in Unreal Engine, as well as an understanding of new features coming in UE5," UE5 being a common abbreviation for the latest version of the Unreal Engine.
Obsidian is currently working on three projects that we know about: early access survival game Grounded, The Outer Worlds 2, and Avowed, the last of which is a first-person fantasy RPG set in the Pillars of Eternity universe. This listing could be for an employee who will go to work on any or all of those games. However, Epic Games only recently put Unreal Engine 5 out in early access and Avowed was announced in July last year, so there's a good chance its development would be too far along now for Obsidian to consider a new engine. As Obsidian's furthest off publicly announced project, The Outer Worlds 2 seems to be the most likely candidate.
As for why you should care about which particular Unreal Engine Obsidian is using for any given project, both Epic and external developers have made some pretty compelling arguments about the visual fidelity it can help developers achieve with less time and fewer resources. It may be a while until Obsidian is ready to share more about The Outer Worlds 2, but hopefully it will bring us some beautiful new alien worlds to explore.
While we wait to hear more, you can check out The Outer Worlds 2's debut trailer from E3 2021.