Ornatrix V3 is x86-only and yes, you have to start C4D with Rosetta to use it.
Ornatrix versions since 4.0.2 switched to ARM.
No, we cannot backport ARM support to V3.
For an unknown reason, Ornatrix won't show up in the viewport in C4D 2025.3 on Windows. I'm not sure about Mac, I don't remember if it had the same problem, but I would be suspicious in general about using Ornatrix with 2025.3.
2025.2 and 2026 have no known problems.