Matcha

Matcha runs macOS Monterey in a melange VM.

Setup

VM noVNC kinda works ok; press the Windows key if you need to switch between windows of the same application by then hitting the backslash ` key.
Install XCode, EFI Agent, meld.
Set the hostname via Apple > System Preferences > Sharing (two places)
Get MAC address from Apple > System Preferences > Networking and update dnsmasq to give out a static IP; renew lease on mac
Allow SSH: Apple > System Preferences > Sharing > check Remote Login; then you can do the usual ssh config, and update /etc/ssh/sshd_config to disallow passwords.

Installation

You can follow thenickdude's awesome guide with these secret sauce bits to get going. I'll add some notes since those might disappear...

Note that thenickdude's Monterey install wasn't working on July 3 2022, as it was pulling the wrong image from Apple. I used Big Sur and once running, immediately upgraded it to Monterey, which went flawlessly.
Set up a OpenCore VM with an unclaimed serial using SMBIOS iMacPro1,1 to match up well enough with my AMD Ryzen 9 3900X 12-core processor.
This helped to mount and access the EFI boot drive.
I used a macOS release of my old fave Meld

See here for more info:

💉 m@cast  [~/apps/macOs-on-proxmox] 
# ^ see readme.txt and install.sh
matcha HOME / apps
EFI Agent > icon in toolbar > EFI drive > mount > browse to OC > config.plist