Running Mac OS 9 under OSX

You could try QEMU https://www.qemu.org
It should run Mac OS 9 https://wiki.qemu.org/Documentation/Platforms/PowerPC

 

Last time, I've been using QEMU, it shipped as an app bundle with a nice GUI. That's why I can't guide you through the installation right now. I'm sure there are tutorials around the web or more experienced users here on MR.

Am I right that you've never been using Homebrew before? (Home)brew is the recommended package manager for macOS nowadays. It has been MacPorts and Fink before Homebrew entered the scene. If you know a bit of Terminal, Homebrew can bring you many software on your Mac just with few simple commands. Though I prefer to compile software from source without a package manager, it's nothing wrong in using homebrew.

https://brew.sh
https://formulae.brew.sh/formula/qemu

If that sounds still greek to you, you can find a link to an older prebuilt version (2.10.1 at the time of writing), see Downloads->X86: wiki.qemu.org/Hosts/Mac
EDIT: Warning, the download on that page takes you to MediaFire that shows up one of those annoying MacKeeper ads, don't download MacKeeper, just QEMU, if you go for the prebuilt app.

This package from here here seems to be more trustworthy and more up-to-date, no MacKeeper ads:
https://www.emaculation.com/forum/viewtopic.php?f=34&t=8848

I guess setting up a working Mac OS 9 in there necessitates to learn a bit more greek. From the link of my first post (the suggested command-line options to install Mac OS 9):

Code:

./qemu-system-ppc -hda <hd image file> -M mac99 -m 256 -cdrom <iso file of installation media> -boot d

Better follow this guide to install Mac OS 9:
https://www.emaculation.com/doku.php/ppc-osx-on-qemu-for-osx