Files in /etc/hotplug.d/iface not run on BThub5 device

Using OpenWrt 19.07.4 on a BThub5 device the scripts in /etc/hotplug.d/iface are never run when interfaces go up or down.

I see several low priority reports in the bug tracker about hotplug.d but none specifically mention the BThub5 device.

Any suggestions on any additional tracing or testing I should try to gain more information for submitting a bug report.

Hotplug troubleshooting