Could be tempting to get my hands on a Power9 so I could dust off some old PowerPC specific projects from the early 2000s but I think converting a MacOS(G3/G4) based application to PowerPC Linux would be too time consuming.
I wouldn’t recommend anyone wanting to track down & use an Itanium based system, unless you have software which runs natively on it & benefits from the compute side. From what I remember there were areas it was snappy vs x86/x64 but that lead was quickly shrinking by the Core era. Same can be said about the G5, if it wasn’t for Freescale thinking they had a hold on Apple when it was known there was always an x86/x64 version of Darwin/OS X… (from what I remember a dual G5 still packed a reasonable compute punch until 2nd gen Core i(aka Sandybridge)
If I had been a member on Teksyndicate back when I was slowly clearing out parts, had a “spare” Amiga 1200 board… more interesting side of “repairing” Amigas, within North America they only seemed popular within the northeast(US/CAN). Anyone I’ve met from the West Coast who had an Amiga were typically from California or Washington.
An easy way to get your hands on a Cyrix based CPU is look for early AMD Geode embedded boxes, they were still based on the Cyrix MMX clone(MediaGX). Geode embedded were common for CNC, remote desktop terminals, industrial and others.