Debian 10 bonding + bridge noIPv4 for kvm guests

Question

I've a big problem with my fresh Debian 10 Installation on my root server at home. I use 2 of the NICs connected to my switch as "bond0" and now I want to add a bridge "br0" for my kvm guests. I don't want to assign an IPv4 adress to either "bond0" or "br0". They should only allow guests to get IPv4 addresses. Sadly, guests only become IPv6 and it works, but I need IPv4 for them and I can't figure out where the problem is.

I enabled IPv4 forwarding in the kernel with echo 1 > /proc/sys/net/ipv4/ip_forward

Here's my /etc/network/interfaces:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eno1
iface eno1 inet manual

# The primary network interface
allow-hotplug eno2
iface eno2 inet manual

#Bonding Interface to HP-Switch for br0
auto bond0
iface bond0 inet manual
        bond_slaves eno1 eno2
        bond_mode 0
        bond_miimon 100
        bond_updelay 200
        bond_downdelay 200

#br0 für KVm/QEMU
auto br0
iface br0 inet manual
        bridge_ports bond0
        bridge_fd 2
        bridge_stp on
        bridge_maxwait 0

# The primary network interface
auto eno3
allow-hotplug eno3
iface eno3 inet static
        address 192.168.223.201/24
        gateway 192.168.223.254
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 192.168.223.254
        dns-search japasp.local