RClone Docker is unable to mount any drive under OpenWRT

I meant absolutely the opposite. Whenever you come across a complex bug, the most optimal strategy is to "divide and conquer" i.e. strip off extra complexity and isolate the very cause of the bug. Docker adds complexity.

Ahh. You have a less complex bug reproducer. I will post right there.

By putting OpenWrt in container you are loosing the granularity. Normally Docker will isolate programs in container from the host network card. Instead, it will create a simulated point-to-point virtual ethernet veth card, assign it a private IP and put it alone in the container network table. The QoS traffic control in the container will most probably manage packet queues of that simulated card. After going out of simulated card those packets will intermix with packets from other software of the rest of the system. If you are happy with that, OK.