SQM fails to start

I'm trying to start SQM on a FriedlyElec ZeroPi with openwrt 19.07.1.

When activating SQM in LuCI I get the following error messages with logread:

Aug  9 17:18:11 user.notice SQM: Starting SQM script: simple.qos on eth0.2, in: 30000 Kbps, out: 10000 Kbps
Aug  9 17:18:11 user.notice SQM: Using generic sqm_start_default function.
Aug  9 17:18:11 user.notice SQM: ERROR: cmd_wrapper: ip: FAILURE (2): /sbin/ip link add name TMP_IFB_4_SQM type ifb
Aug  9 17:18:11 user.notice SQM: ERROR: cmd_wrapper: ip: LAST ERROR: RTNETLINK answers: Not supported
Aug  9 17:18:11 user.notice SQM: ERROR: cmd_wrapper: ip: FAILURE (2): /sbin/ip link add name TMP_IFB_4_SQM type ifb
Aug  9 17:18:11 user.notice SQM: ERROR: cmd_wrapper: ip: LAST ERROR: RTNETLINK answers: Not supported

I don't know how to interpret these lines:

  • does it mean: the hardware/driver does not support SQM ?
  • does it mean: I miss some packages for SQM ?

I appreciate any hint.