@thiscantbeserious Unfortunately I don’t think my findings will be directly helpful for you as I was not encountering the same error, but they may help point you in the right direction. The issue with mDNS, as I recall, is that qemu needs to have the interface have trustGuestRxFilters=‘yes’ set for mDNS traffic to flow through. I was not able to find a way to do that for LXD VMs as part of the VM’s configuration, but what I was able to do was to tell systemd to change the settings of the network interfaces when they are brought up so that all multicast traffic flows through. On my system, which is a Ubuntu Focal host, I created a file called /etc/systemd/network/lxd-vm-multicast.network with the following content:
[Match]
Name=mac*
[Link]
AllMulticast=true
This allowed mDNS traffic to flow into the VM, which is what I needed to get the Chromecast integration working (and is likely required for others). The approach I took may be a bit blunt, but it works for my use case as Home Assistant is the only VM that I run and it has been working well for me ever since. I am always open to constructive criticism and I am by no means an expert on this topic, so happy to get any feedback about how I could have done this better if you or anyone else has any better ideas. It took me a lot of Googling around to figure this out, so hopefully some of the keywords above help you out (I made some progress searching “trustGuestRxFilters”).