I seriously doubt escape simulator is well enough optimized to run a Myst board with anything resembling decent framerate. RealMyst and RealMyst Masterpiece Edition already exist anyways.

I wouldn't mind some Myst universe themed rooms though!

Some Myst themed stuff here is, as stated, pretty much inevitable eventually.
Heck, I may even consider making some.

Though right now my focus hasn't exactly been on making fan content, mostly my own original stuff not tied to others' IP that I can actually legally sell, and the Myst fan content queue of mine is fairly full of other projects like eventual Uru fan ages, BUT I'm a big fan of the puzzle/adventure genre and want to make content in it, and I am looking at testing out Escape Simulator soon to see how flexible its editor is.

I've got a whole checklist. Seems loading custom audio and textured custom models is a thing, as is custom scripting for interactions not included. Those are the three biggest things, and it seems that this game supports all three. Which means I may seriously consider it as an option when building worlds in the future. The main downside of doing that vs. using say, Adventure Creator in Unity, obviously, is the barrier to access. The worlds created would only be accessible to those who own Escape Simulator.

Which makes them less than ideally accessible to the world. I'd prefer to have the fan content available for free to anyone online. But... a third port of some of the designs made first in standalone Unity game form and Myst Online (Uru) versions, not out of the question that this could also be an output goal. The graphics, that's possible I think to make things look similar in all three using the same source models and textures. Even baked lighting. But figuring out implementing similar interactions and puzzle concepts across all three is not going to be trivial.

That said, Korman - the toolkit in Blender that supports Uru output - is way harder to work with than anything I'd expect to see in Escape Simulator's editor. Even Unity's editor with addons, probably is significantly trickier. It's certainly possible the easiest way to make puzzle gameworlds will be here, and that even places I built for other spots first will end up reaching here first simply due to the relative simplicity of implementation in this system.

As for Myst, both Myst and Riven now have great VR versions, realtime 3d Unreal Engine based remakes. Worth a look in the meantime.

Myst's 2020s version is polished graphically in a thorough overhaul that makes RM:ME's updates look comparatively half-baked. Yet as with most of these remakes, there are two steps forward and one back. In a sense. It all looks gorgeous visually, has VR support, but it removed the ending Rime age from RealMyst and RM:ME, and the character animation is janky. Something much improved on with the VR remake of Riven.

Riven's remake in particular is pretty awesome, they took the setting and contents of the design and messed with it in somewhat significant ways and yet it still remarkably holds together really well, as nearly every change is thought out well. The puzzles are conceptually similar but a lot of that is altered enough to really make you think it through differently, so gameplay flows, scales better in puzzle design terms, than the original, even if in a few spots the changes strain narrative credulity slightly. Graphically, a huge improvement, and there are new areas in every age with the original art director, and the original musician of Riven filling in those new spaces in visual and sound design so they fit with everything else. It somehow shakes up many things yet retains the fascinating core of the game and is true to that while also meaningfully extending it and making it more immersive and beautiful than ever.

As for other titles in the Myst series worth revisiting:
Myst III: Exile has a high res 4k mod now. It uses a custom AI upscaling model, and while some of the sites you can find it on look sketchy, the mod is VERY real and it's a 17gb thing that gives the game far more visual fidelity. I know Exile has its detractors who find it 'small' in some sense and not the giant expansion in scope people wanted after Riven and found the 'lesson age' conceit a cop out, but the game's 'smallness' also makes its story personal. Less about a societal drama and more a focused story of one person who was wronged. And it is very much a game worth revisiting at this point given the recent graphical improvement.

Uru likewise, was an odd and messy game, very uneven with janky physics and yet some beautiful scenes [though constrained by 2000s realtime 3d tech] and some fantastic sound design, and some puzzle sequences that are well thought out [ie, Ahnonay, Kadish Tolesa] and some that suck [Eder Gira's basket puzzle] and numerous scattered problems out of the gate that only were compounded as it was shut down and then reopened multiple times. But if you hadn't played it in its first two runs, or you did, but not since, now isn't the worst time to revisit it. Firstly, because it is 100% freeware and has been since it reopened that way about a decade ago. You can donate to offset cost of running the servers, but it's very much optional, and while Cyan has stopped actively expanding it, a ton of fans have built fan ages and built up an entire pipeline for making them and curating the best ones, such that there are about ten fan ages in Uru at this point and a lot of bug fixes and subtle improvements. One fan setting in particular, Kalamee, is actually adapted by fans off of old Cyan concept art and puzzle design docs - the "Intangibles Project" with a bunch of unfinished designs, that got leaked to the fandom in hopes of fans completing what the studio couldn't justify completing themselves. The rate of new ages added to Uru is usually about 3-4 a year by now. Not fast, but not bad given that it's the output of a dozen or so volunteers working on it as a part time hobby. The flow of fan ages added starting around 2020 is a good reason to revisit it, even if some fan ages are not strong in all aspects, basically all of them have merit of some sort in some area or areas that got them approved for inclusion on Cyan's Uru server.