this powered hub; Sipolar A-165 is 2.4a per port
I missed per-port when I previously checked the specs. I must have been looking at a different spec because this one...
https://www.aliexpress.com/item/33008148011.htmlalso says 2.1A per port.
What happens when you have 10 plugged in? Do 9 work? That would indicate a software limitation. A power problem
would cause them all to fail.
You could try adding other USB devices to the hub so see if you can connect 10 devices simultaneoulsly if they aren't
all miners. That would determine if it's a bfgminer limitation. Try a second hub to determine if it's a hub limitation.
I'm also a bit skeptical, "per port" may not necessarilly mean "all ports simultaneously".
Also as mentioned the Moonlander is just a toy so experience with multiple units is likely limited.