https://linuxways.net/debian/how-to-install-kvm-on-debian-12/

# Checks Intel
grep -e 'vmx' /proc/cpuinfo
# Checks AMD-V
grep -e 'svm' /proc/cpuinfo
# Check both Intel and AMD
grep -E --color=auto 'vmx|svm|0xc0f' /proc/cpuinfo
lscpu | grep Virtualization
lsmod | grep kvm
sudo modprobe vhost_net
lsmod | grep vhost
cat /sys/module/kvm_amd/parameters/nested

Debian /usr/bin/qemu-system-x86_64
Almalinux /usr/libexec/qemu-kvm

sudo apt install libvirt-daemon-system qemu-kvm qemu-system libvirt-clients bridge-utils libguestfs-tools genisoimage virtinst libosinfo-bin virt-viewer -y
sudo apt install virt-manager -y
sudo systemctl start libvirtd
sudo systemctl enable --now libvirtd
# ADD username to groups as your own user - NOT root
sudo usermod -a -G libvirt,kvm $USER
sudo reboot

**WARNING** Be on server as root. nmtui for graphical. RECOMMENDED using nmtui
sudo virsh net-list --all
# sudo virsh net-start host-bridge
# sudo virsh net-autostart host-bridge
sudo modprobe vhost_net
sudo vi /etc/modules
# Add vhost_net

______________________________________________________________________________
#Be on server as root. nmtui for graphical. RECOMMENDED using nmtui - see kvm-debian-ovmf-uefi-boot-fix.pdf
sudo vi /etc/libvirt/qemu/networkshost-bridge.xml
#Add the following lines:
<network>
  <name>host-bridge</name>
  <forward mode="bridge"/>
  <bridge name="br0"/>
</network>
#Run the following commands to start the newly created bridge and make it as default bridge for VMs:
sudo virsh net-define /etc/libvirt/qemu/networkshost-bridge.xml
sudo virsh net-autostart host-bridge
# virsh net-destroy default
# virsh net-undefine default

# create file if not created
sudo vi /etc/sysctl.d/bridge.conf
# add the following lines
net.bridge.bridge-nf-call-ip6tables=0
net.bridge.bridge-nf-call-iptables=0
net.bridge.bridge-nf-call-arptables=0
# create file if not created
sudo vi /etc/udev/rules.d/99-bridge.rules
# add the following lines
ACTION=="add", SUBSYSTEM=="module", KERNEL=="br_netfilter", RUN+="/sbin/sysctl -p /etc/sysctl.d/bridge.conf"
# REBOOT SYSTEM

----------------------------------------------------------------------
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html-single/configuring_and_managing_networking/index#proc_configuring-a-network-bridge-by-using-nmtui_configuring-a-network-bridge
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html-single/configuring_and_managing_networking/index#configuring-a-network-bridge-by-using-nm-connection-editor_configuring-a-network-bridge
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html-single/configuring_and_managing_networking/index#proc_configuring-a-network-bridge-by-using-nmstatectl_configuring-a-network-bridge

su - root
nmcli con show
ip link
virsh net-list --all
nmcli con del "Wired connection 1" # or delete UUID
nmcli con add type bridge autoconnect yes con-name br0 ifname br0 stp no
nmcli con add type bridge-slave autoconnect yes con-name eno1 ifname eno1 master br0
nmcli con mod br0 ipv4.addresses 192.168.1.222/24 ipv4.method manual
nmcli con mod br0 ipv4.gateway 192.168.1.131
nmcli con mod br0 ipv4.dns "192.168.1.140 192.168.1.141 192.168.1.143 192.168.1.144"
nmcli con mod br0 bridge.stp
# nmcli con mod $connectionName ipv4.ignore-auto-dns yes
nmcli con mod br0 bridge.stp no
service NetworkManager restart
nmcli device show
nmcli -f bridge con show br0