Comment 1 for bug 1618463

sudo add-apt-repository ppa:ci-train-ppa-service/2038
sudo apt update
sudo apt dist-upgrade

After that please regenerate persistent configuration for your qeth device, e.g.:

$ sudo chzdev -p -d 600
$ sudo chzdev -p -e 600 bridge_role=primary
$ sudo update-initramfs -u

undo any other manual changes to set bridge_role to primary, and finally reboot to test the packages with a proposed fix for your issue.

Please note packages are pending publication, however should be available shortly.