I am experiencing connectivity issues on my Devuan host machine when starting a VM using virt-manager.
The VM is configured to use default virbr0 NAT network. It is getting usual 192.168.122.x IP from DHCP.

Upon starting the VM, a new network interface (vnet1) is created in the host. The routing table changes on Devuan host, becoming the default route:
$ ip route
0.0.0.0 dev vnet2 scope link
default dev vnet2 scope link
default via 192.168.1.1 dev eth0
(...)
This change leads to loss of internet connectivity on the host, and it prevents internet from ever working in the guest as well, as it tries to route traffic through the vnet interface, which does not have a valid internet connection. In the example above, we can see vnet2 because I tried adding another NIC to the VM, every time result is the same, guest NIC is activated, vnet is spawned, changing default route for entire host.

I don't know why this happens, I did not experience it on Debian host from which I just migrated.

When all VMs are closed, or their NICs are removed, internet works normally in Devuan host:

$ ip route
default via 192.168.1.1 dev eth0
(...)

Expected behaviour is of course virbr0 NAT network working normally without affecting the host's internet access.
Any insights appreciated!