I’m getting this error while trying to vagrant up on my project for the day (no other Vagrant projects are active, and all have been correctly destroyed)

An error occurred while executing the action on the '...'
machine. Please handle this error then try again:

Error while activating network: Call to virNetworkCreate failed: internal error: Child process (VIR_BRIDGE_NAME=virbr1 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/vagrant-libvirt.conf --leasefile-ro --dhcp-script=/usr/libexec/libvirt_leaseshelper) unexpected exit status 2: 
dnsmasq: failed to create listening socket for 192.168.121.1: Address already in use

According to ip addr, there is no “192.168.121.1”, so it cannot possibly be already in use. virsh net-list is empty. (virsh net-dumpxml vagrant-libvirt returns a “not found” error, and virsh net-dump as likely generated by ChatGPT in Google results isn’t a real command) dnsmasq is running on the host, but is correctly configured to bind to lo only (so, 127.0.0.1:53 and no other address).

And probably the biggest note, the one everyone hates reading, and the one I hate writing: I changed nothing, this worked with no problems yesterday, and is now broken with no explanation today.

Any ideas where to even start looking on this one, or should I just purge all traces of vagrant and libvirt from my system and start from zero again? There is no data in libvirt or vagrant that cannot be regenerated quickly, so “nuke and pave” is a safe option in this case.