I might have another suggestion, but I have to finish some testing tomorrow for what I started in the late afternoon.
Somehow, some way, people have gotten all kinds of OS X and macOS versions to run in UTM. All without, apparently, a Mac BIOS. Since I have legal disks for OS 9 and Snow Leopard Server, I downloaded pre-built virtual machines to see how well they run. Saves me the trouble of trying to install them myself, which isn't easy.
I have a feeling SL Server isn't going to be very fast. Probably about the same as my Win XP image. And I think that OS is too old for CS5.
Haven't found any later Intel versions of macOS for UTM already built. Big Sur or Sierra would be a better fit for CS5, if they exist.