Guess what, folks?
It finally arrived. I've put it through its paces and here's the verdict. Note that I only dedicated about ten minutes to each fort, because I just don't have that much time:
Dawnthunder, from Superdorf's, held steady at 11 FPS. Not precisely playable, but things were still happening.
Failcannon, from Paaaad, wound up at 34 FPS as the few remaining dwarves braved a rapidly-flooding fortress and tried to store things in the stockpile. After a little while, another Forgotten Beast showed up. Things were probably going to get ugly.
Archcrystal, from NordicNooob, wobbled between 21 and 30 FPS, but mostly stayed around 25. Dwarves were happily going about their business. Also, that's a lot of clear glass block walls.
Whew. I honestly had thought that it wasn't going to wind up happening. It also runs Witcher 3 on ultra at 60 FPS, but honestly, we're not here to talk about that.
It's a Dell G3 with the i5 processor. I'm writing a full review for posting elsewhere, but I'm not really here to advertise for Dell.
Edit: Turned off the Turbo Boost feature. Some programs run better afterwards, possibly due to less overheating of the system. Dwarf Fortress isn't one of them. A cursory re-test (only a minute or two each) shows Failcannon at 23 FPS, Archcrystal at about 15, and Dawnthunder at 6. Turbo Boost is essential for Dwarf Fortress, apparently, and I intend to leave it off because it increases processor temperature enough that it might shorten the longevity of the computer, and I'm in no position to replace it if it dies.
FURTHER EDIT: Also, apparently Turbo Boost is glitched, because I achieved better benchmarks and frame rates on everything EXCEPT Dwarf Fortress with Turbo Boost OFF.