Snd-aloop in LXC container

I need to use the ALSA snd-aloop module so I tried to load it in a LXC Ubuntu container via modprobe. That failed, because modprobe insisted on looking into the host’s /lib/modules (with no snd-aloop) instead of the container’s (with snd-aloop). I found that’s normal behavior and that you’re supposed to load a module in the host. But even though I installed alsa-libs and alsa-utils using opkg, snd-aloop is missing in the host. Supposedly, by putting lxc.cap.keep = sys_module into a container’s config, you can load modules via modprobe in the container, but unfortunately it didn’t do anything in my case. When I tried to copy the snd-aloop.ko from container to the host, I got an error 1 module could not be probed. Is there a way to achieve this?