I managed to get what I need by compiling a new (hopefully) compatible set of modules and installing by hands only the needed ones. Here are the steps I followed, executed directly on the AXON as root:
v=$(uname -r) cd /usr/src wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-$v.tar.xz tar xf linux-$v.tar.xz cd linux-$v gzip -dc /proc/config.gz > .config apt install libncurses5-dev bc # Customize the kernel to your needs. In my case I enabled the # snd-usb-audio module that, in cascade, enabled other sound stuff. make menuconfig # Build and install *only* the new modules. make modules mkdir -p /lib/modules/$v/kernel/sound/usb cp sound/usb/*.ko /lib/modules/$v/kernel/sound/usb/ cp sound/core/snd-*.ko /lib/modules/$v/kernel/sound/core/ depmod # Not strictly needed, but forbidding future axon-kernel upgrades # could avoid potential hard-to-debug problems. apt-mark hold axon-kernel