How do I download Rosetta (PPC to Intel)?

The original Rosetta has ceased to work many years and OS versions ago... in fact about a decade. The last version of Mac OS X that included it was Snow Leopard 10.6.8. It was removed in Lion 10.7, released in 2011.

There is no way you can make it work in Big Sur.

AppleRules1 wrote:

I have an iMac running macOS Big Sur and i need to run a PowerPC application on my Mac. is Rosetta still on Apple servers?

PowerPC application ancient history here.

I will add 32-bit applications will not run on 64-bit only macOS Big Sur even if the original "rosetta" was available.

Maybe you have a local Apple Macintosh type club or user group, who may have a current interest in PPC.

ex. The Silicon Valley Macintosh User Group - General Information

Your bet bet is to buy a PPC mac.

Nope.