I get this error
DKMS: install completed.
Building initial module for 4.18.0-0.bpo.1-amd64
/var/lib/dkms/zfs/0.7.9/build/configure: line 13069: dpkg-architecture: command not found
configure: error:
*** Please make sure the kmod spl devel <kernel> package for your
*** distribution is installed then try again. If that fails you
*** can specify the location of the spl objects with the
*** '--with-spl-obj=PATH' option. Failed to find spl_config.h in
*** any of the following:
/usr/src/spl-0.7.9/4.18.0-0.bpo.1-amd64
/usr/src/spl-0.7.9
Error! Bad return status for module build on kernel: 4.18.0-0.bpo.1-amd64 (x86_64)
Consult /var/lib/dkms/zfs/0.7.9/build/make.log for more information.
EDIT: found this
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=909096