So in the image https://am.mirrors.kernel.org/opensuse/distribution/leap/15.5/appliances/openSUSE-Leap-15.5-Minimal-VM.x86_64-kvm-and-xen.qcow2
uname -a
Linux localhost 5.14.21-150500.55.7-default #1 SMP PREEMPT_DYNAMIC Mon Jul 10 18:53:13 UTC 2023 (4204a3a) x86_64 x86_64 x86_64 GNU/Linux
with all stock, except the DISABLED firewall, the lxc is workig and getting the ip
installing the 55.22
zypper search -s kernel-default-5.14.21-150500.55.22.1
uname -a
Linux localhost 5.14.21-150500.55.22-default #1 SMP PREEMPT_DYNAMIC Wed Sep 6 08:41:01 UTC 2023 (1e6fbaf) x86_64 x86_64 x86_64 GNU/Linux
container2 | RUNNING | 10.215.220.243 (eth0)
So is working also with the 55.22 kernel.
of course if I enable the firewall it will no longer get the ip.