sudo pacman -S libvirt nftables

 ✘  ~  cat br10.xml 
<network>
  <name>br10</name>
  <uuid>4c2ce191-a0e3-4916-842e-a7cdc2012332</uuid>
  <forward mode='nat'>
    <nat>
      <port start='1024' end='65535'/>
    </nat>
  </forward>
  <bridge name='br10' stp='on' delay='0'/>
  <mac address='52:54:00:5f:d2:40'/>
  <ip address='172.18.0.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='172.18.0.100' end='172.18.0.200'/>
    </dhcp>
  </ip>
</network>

sudo virsh net-define br10.xml

sudo virsh net-list --all

 sudo virsh net-start br10

 sudo virt-install --name debian11 --memory 2048 --disk size=4 --cdrom Downloads/debian-11.0.0-amd64-netinst.iso --network bridge=br10

sudo virsh start debian11