This is macOS Catalina running in QEMU on top of KDE Neon Linux. I used an easy to follow how-to at Computing For Geeks that uses the macOS-Simple-KVM project on Github.
MacOS seems to think it's a Late 2009 iMac 27" Core 2 Duo, since two cores are allocated to it by default. RAM and cores allocated can be changed by editing the script. I have increased the amount of RAM to 3GB. I seem to have an issue with Step 4 of the guide, adding the VM to Virt-Manager. It won't let me add the right disk image in storage so I have to start the VM from ~/macOS-Simple-KVM$ ./basic.sh every time. And Bridged Networking is a bit fiddly, so right now it can connect to the net, but not my local network. I have not thought of a particular use for this VM yet, but I am sure it might come in handy if I need a macOS-only app at some point.