How can I tell if my Mac Wifi adapter supports "ap mode"
As far as I know all Macs sold within the last many years support AP mode.
I doubt that your problem is that your WiFi card does not support AP mode, rather it is the fact that you're operating on a virtual network interface inside VirtualBox or Docker - and that doesn't allow exposing such features to the guest OS.
Instead remove the WiFi interface from the host (i.e. it should not "grab" it over USB/PCIe or whatever - it should not load its drivers). Then expose it to the guest as a USB/PCIe device, and let it grab it.