No network configured in new lxc-containers running Debian

When I install a new guest running Debian with

lxc-create lxc-create -n net-test-stable -t download

and answer ‘debian’, ‘bullseye’ and ‘amd64’ the guest doesn’t have a configured network when it is started.

It works if I choose to download Ubuntu Jammy or Ubuntu Focal.

By “doesn’t have a configured network” I mean that ip a s shows two interfaces ‘lo’ and ‘eth0’ and only lo has an ip, namely 127.0.0.1. If I manually configure eth0 with e.g. ip a a 10.0.3.99/24 dev eth0; ip r a default via eth0 and put “nameserver 10.0.3.1” in /etc/resolv.conf, everything seems to work.
(dhclient is not installed so using that to get an ip isn’t an option)

It used to work on that machine, I have a container with Debian bullseye I installed in February, I might have installed some since, but they have been destroyed so I don’t have any leftovers I can see the date on.

The machine I’m on runs Debian stable, and has lxc installed from the package manager, and it hasn’t been upgraded since February (since the machine was upgraded from Debian Buster to Debian Bullseye sometime last year actually, but I’m pointing to February as it worked then). What has happened? And how do I fix it?