Mach's ohne libvirt, dann sieht man auch, wo es hakt.
#!/bin/bash
USERID=towo
INTERFACE=$(sudo /usr/bin/tunctl -b -u $USERID -t tap2)
KVM_GUEST_NAME="Android"
sudo brctl addif bri0 $INTERFACE
sudo ip link set "$INTERFACE" master "bri0" up
qemu-system-x86_64 \
-m 4096 \
-bios /home/towo/ovmf-x64/OVMF-pure-efi.fd \
-accel kvm \
-name Linux \
-smp cores=6,sockets=1 \
-cpu EPYC \
-device virtio-vga,virgl=on \
-display gtk,gl=on,full-screen=on \
-machine type=q35 \
-device AC97 \
-net nic,macaddr=52:54:00:12:34:62,model=virtio \
-net tap,ifname=$INTERFACE,script=no,downscript=no \
-drive file=/home/towo/daten2/image/lin.qcow2,cache=none,if=virtio \
sudo tunctl -d $INTERFACE
Das funktioniert hier astrein.