Cannot tether with Nikon NZ9 even though the most recent updates supports the Z9

"The software says it is only available through something called Rosetta."

See this article for how to run tethered capture on newer Apple Silicon Macs:

https://helpx.adobe.com/lightroom-classic/kb/tether-support-apple-silicon-devices.html

If that does't work for you, please provide much more detail about what you see, including screenshots of any error messages. Also, do the LR menu command Help > System Info and copy/paste the entire contents here so we can see exactly which versions of hardware and software LR thinks you're running.

Nikon provides the tethering library for LR, and they haven't bothered to provide an updated version that runs natively on Apple Silicon Macs, even though they've been out for over two years.

Is the old MacBook not MACOS Ventura?

And the new MacStudio would be Ventura?

And for each, what version of LrC? 12.2?