I use br0 for a couple of DNS servers and NextCloud, but starting a few months ago every time I reboot the server the br0 network is removed.
Here is the command I used to recreate it after it happened the first time:
docker network create -d ipvlan --subnet=192.168.1.0/24 --gateway=192.168.1.254 --ipv6 --subnet=2001:5xx:7exx::/48 -o parent=br0 br0
I use IPv6 for a few things. I initially tried to use macvlan in the command, but changed to ipvlan, as the docker custom network type is set to ipvlan.
I saw a few people talking about shim network settings being the issue, but I'm not sure if that applies in my situation.
I've attached my diagnostics and system log from this morning, which was my last reboot for an upgrade to 6.12.3, and the last time I saw the issue.
server-diagnostics-20230717-0830.zip
server-syslog-20230717-1531.zip