This is more or less just a note to self.
apk add qemu-modules
incus create images:freebsd/15.0 "$container" --vm
incus config set "$container" security.secureboot=false
incus start "$container"
Also, FreeBSD doesn’t come with VirtIO input drivers that work with incus, so:
incus config set "$container" raw.qemu.conf - << EOF
[device "fbsd_usb_kbd"]
driver = "usb-kbd"
[device "fbsd_usb_tablet"]
driver = "usb-tablet"
EOF
The qemu-guest-agent appears to be irrelevant here.
Then,
incus console caprika --type=vga