I remember. So,more or less,it should be something like this :
qemu-system-arm \
-enable-kvm -serial stdio \
-m 512 -M virt -cpu cortex-a15 \
-drive file=/mnt/fisso/OS/FreeBSD/FreeBSD-13.2.qcow2,id=virtio-blk,if=none \
-device virtio-blk,drive=virtio-blk \
-device virtio-net,netdev=net0,mac="52:54:00:12:34:55" \
-smbios type=2 -nodefaults \
-netdev type=user,id=net0 \
-bios "OVMF_CODE.fd"
-append "earlyprintk=ttyAMA0 console=ttyAMA0 mem=512M \
virtio_mmio.device=1M@0x4e000000:74:0 \
virtio_mmio.device=1M@0x4e100000:75:1 \
root=/dev/vda rw ip=dhcp --no-log"
The problem is that devuan does not offer the proper OVMF file,as you can see :
# apt search ovmf
Sorting... Done
Full Text Search... Done
ovmf/stable 2020.11-2+deb11u1 all
UEFI firmware for 64-bit x86 virtual machines
ovmf-ia32/stable 2020.11-2+deb11u1 all
UEFI firmware for 32-bit x86 virtual machines
These UEFI files are for x86-64 bit,so they are not good for armhf. Where I can find the right ones ?