Tente isto:
Para desabilitar permanentemente o Network Manager:
Abra um terminal
Pressione Ctrl + Alt + T
Execute:
exec sudo -i
systemctl stop NetworkManager.service
systemctl disable NetworkManager.service
mv /lib/systemd/system/NetworkManager.service NetworkManager.service.res
Para renegociar o Network Manager:
Abra um terminal
Pressione Ctrl + Alt + T
Execute:
exec sudo -i
mv /lib/systemd/system/NetworkManager.service.res NetworkManager.service
systemctl enable NetworkManager.service
systemctl start NetworkManager.service