Yes, unfortunately, a stable Nuendo 1.x or 2.x system under Mac OS9 was not meant to be...
I was a 50% owner in a company that was endorsed by Steinberg to sell Nuendo PC dual Pentium III systems (with blue lucite cases) via Sam Ash distribution in NY. The Tower PCs were outfitted with RME 9652 Cards and Nuendo 1.x This was the first time that PC platform product development was was ahead as compared to the mac. Nuendo, as I remember, was announced for both Silcon Graphics workstations and PCs with Windows NT.
Since Nuendo was originally released as a Windows-only product, the Mac OS Nuendo 1.5 version would have to wait a full year (in 2001) to be compiled from the "portable framework" that is was developed on. Meaning in 2001, Nuendo 1.x for Mac OS 9 was basically a super-buggy application that crashed constantly while the PC version ran on dual PIIIs rock solid all day long. As far as Nuendo 2, Mac OS 9 was done by then.
I was very sad at the time, because my heart was in the OS 9 camp. Many Mac OS 9 project studios that switched to Nuendo eventually switched back VST 5/32 after a few months, since it was just not ready for prime time in Mac OS 9. I strongly believe that VST 5/32 is as good as it gets for Steinberg fans under OS 9. At the time in 2001, Nuendo was absolutely amazing on a PC with a multiple undo stack, dual-CPU support, and a bunch of other features, but it still lagged when triggering Virtual instruments with a controller. This was my main gripe with PCs, we were enjoying zero latency MIDI via keyboard controllers since Mac OS 8.1. Also, Directx plugins on the windows side lacked the ability for recording automation (another thing we were enjoying in the mac arena).
But time marched on, in the end, CPUs got fast enough to crunch the Mircrosoft spaghetti code that they called "an operating system" As as these systems parsed thru the fu*k&^g database nightmare that they called a registry, a DAW on PC platform became quite use-able. It's was just a known fact, like today, that if your Studio PCs is working well... don't install anything new, don't update anything, ALWAYS make a restore point, etc. (what a way to live). Now Apple has followed suite by breaking things for musicians with every OS update.... who knows, maybe Apple will announce their big plans to add a registry to Mac OS as a new great feature in 2024.