After spending much time playing around with qemu’s settings trying to get Ubuntu for amd64 to boot up, I stumbled across UTM (Releases · utmapp/UTM · GitHub) that had qemu compiled in. Using this I was able to get Ubuntu 20.04.02 desktop installed and running with 2 cores. It boots slowly, but after that it allows me to build legacy apps that require x64. I took a look at ACVM, but there was not an easy way to select x86_x64 emulation