networking - Where is the configuration file of a lxc container?

I installed lxd to use linux containers. For some reason I keep using lxc commands to install and start my containers. Since lxd seems to be close to lxc maybe there is a reason for that (but it is not clear).

I wanted to bind two lxc containers to two different bridges, different from the default lxcbr0 one. I created br1 and br2 and gave them IP addresses. They work fine and are pingable.

I am now trying to locate the place where I should change the configuration of my containers (cont1 and cont2) in order to have their eth0 (the interface name can be kept the same for each of those guests) bound to respectively br1 and br2.

The documentation states that

Then, specify the host's bridge in the container configuration file in
place of lxcbr0, for instance

Where is this configuration file?

At the top of this documentation page, there is information about configuration files:

The following configuration files are consulted by LXC. For privileged
use, they are found under /etc/lxc, while for unprivileged use they
are under ~/.config/lxc.

lxc.conf may optionally specify alternate values for several lxc
settings, including the lxcpath, the default configuration, cgroups to

use, a cgroup creation pattern, and storage backend settings for lvm
and zfs.

default.conf specifies configuration which every newly created
container should contain. This usually contains at least a network
section, and, for unprivileged users, an id mapping section

lxc-usernet.conf specifies how unprivileged users may connect their
containers to the host-owned network.

lxc.conf and default.conf are both under /etc/lxc and
$HOME/.config/lxc, while lxc-usernet.conf is only host-wide.

By default, containers are located under /var/lib/lxc for the root
user, and $HOME/.local/share/lxc otherwise. The location can be
specified for all lxc commands using the "-P|--lxcpath" argument.

If I read it correctly, it does not indicate where the container config file is.

The configuration I would like to add for cont1 is

lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = br1
lxc.network.name = eth0
lxc.network.ipv4 = 10.10.11.0/24
lxc.network.ipv4.gateway = 10.10.11.11

and I tried to put it in the files /etc/lxc/cont1/config and /var/lib/lxc/cont1/config but none was taken into account: the container does not start, failing to bring up the networking. It works fine with the default config using lxcbr0.