I'm maintaining a gallery of split mechanical keyboards, including the Ultimate Hacking Keyboard. Hopefully it's helpful for a quick overview of the options that exist. Many of these keyboards are DIY (available as a kit, or sometimes just a PCB and case plan), but some are available assembled. https://aposymbiont.github.io/split-keyboards/ (There's also https://jhelvy.shinyapps.io/splitkbcompare/ for direct comparis…
no wrist rest, or a hard plastic or wood one is leaving a lot of ergonomics, uh, off the table.