I enjoy running old OSes. Recently (June 2025), I discovered 86Box. I had previously used VirtualBox years ago, but discovered it would only run OSes that use the same processor as my iMac. Having an M3 iMac, it cannot run the Intel OSes. So I'm using 86Box instead.
86Box can be downloaded here. Select the macOS one. It is compatible with both Intel and Apple processors.
The folder where 86Box.app is placed is important. It will save its "86box.cfg" file and "nvr" folder in it.
So, when creating a new virtual machine, create a folder for it and make a copy of 86Box.app in it. Every machine you create should be in its own folder and have its own copy of 86Box.app.
You will also need the various roms that allow 86Box to emulate real PCs. They can be downloaded from GitHub (select the zip file at the end).
You may then put them here : "~/Library/Application Support/net.86box.86Box/roms".
To do that, right click the Finder in the dock, select "Go to folder...", and enter "~/Library/Application Support/". Create the "net.86box.86Box" folder and place the roms folder in it after renaming it to "roms".
Since 86Box is not officially signed by Apple, it means you will get a warning when first opening it. After you get the warning, just open Settings > Privacy & Security and open the app from there.
How to do the PC keys on a Mac keyboard :
So, you can press "fn + ctrl + Right Arrow" to release the mouse after clicking in the window.
The F keys can be done by pressing the fn key.
So, "Ctrl + Alt + Delete" is done with "fn + ctrl + alt + Backspace".
To get networking to work at all, you must leave the first network card set to "None" and use the second one instead.
I have set up machines in 86Box and made tutorials for them :