$ mkdir testdir
$ fetch https://XXXXX/mini-memdisk.img
$ fetch https://bapt.nours.eu/memdisk

Create a ipxe script

Add in testdir a freebsd.ipxe script

#!ipxe
initrd tftp://10.0.2.2/mini-memstick.img
chain tftp://10.0.2.2/memdisk harddisk raw

install qemu and ipxe

$ pkg install ipxe qemu

boot qemu

$ cd testdir
$ qemu-system-x86_64 -boot n -m 4g -cdrom /usr/local/share/ipxe/ipxe.iso -device virtio-net,netdev=n1 -netdev user,id=n1,tftp=$(pwd),bootfile=/freebsd.ipxe