in debian/rules for this package there is hardcoded dependencies to x86_64, this makes compiling this package on arm impossible
rule lines:
debian/rules: cp obj-x86_64-linux-gnu/drivers/ipoe/driver/ipoe.ko debian/tmp/lib/modules/4.19.58-amd64-vyos/extra/ debian/rules: cp obj-x86_64-linux-gnu/drivers/vlan_mon/driver/vlan_mon.ko debian/tmp/lib/modules/4.19.58-amd64-vyos/extra/ debian/rules: dh_auto_clean -- rm -rf obj-x86_64-linux-gnu
this directory is on my armhf called: obj-arm-linux-gnueabihf
a way to reproduce is to build the reository on an armhf system, eg. raspberry pi