Further experimentation. First, I say again that on Windows 11, NetBIOS works on adapter 2 as expected.
Setting Promiscuous mode has no effect, as far as I can tell.
Even TCP/IP on Adapter 2 does not work in Linux. I can swap adapter type, it makes no difference. And If I put NetBIOS on Adapter 1, it does work in Linux. But I have to have the adapter in bridged mode, so I have to choose the adapter. That means not supporting WiFi.
This sounds like a bug in VirtualBox. Adapter 2 works in Windows, but not in Linux.