Bullseye OOB systemd-networkd : https://rcn-ee.net/rootfs/debian-armhf/2021-09-22/bone-debian-11-iot-armhf-2021-09-22-4gb.img.xz

Bullseye systemd-networkd FAQ:

File Locations:

root@BeagleBone:~# cat /etc/systemd/network/
eth0.network   usb0.network   usb1.network   wlan0.network 

root@BeagleBone:~# cat /etc/wpa_supplicant/wpa_supplicant-wlan0.conf

root@BeagleBone:~# ls /etc/bbb.io/templates/
eth0-DHCP.network	 usb1-DHCP.network	  wpa_supplicant-wlan0.conf
usb0-DHCP.network	 usb1-DHCPServer.network
usb0-DHCPServer.network  wlan0-DHCP.network

Windows ICS: 
cp -v /etc/bbb.io/templates/usb0-DHCP.network /etc/systemd/network/usb0.network

eth0.network

[Match]
Name=eth0
Type=ether

[Link]
RequiredForOnline=no

[Network]
DHCP=ipv4

TODO:

Crazy MAC addressing based on mac0

Something to call: when wifi module detecte..
sudo systemctl enable wpa_supplicant@wlan0
sudo systemctl start wpa_supplicant@wlan0
* When microSD goes from Non-WiFi -> WiFi (enable it) -> Non-Wifi (auto disable it)  otheriwse systemd waits for wlan0 to fail on non-wifi board..

udev rule to start wl1835 tether..

usb0-DHCP.network

[Match]
Name=usb0

[Link]
RequiredForOnline=no
#MACAddress=

[Network]
DHCP=ipv4

usb0.network

[Match]
Name=usb0

[Link]
RequiredForOnline=no
#MACAddress=

[Network]
DHCP=no
Address=192.168.7.2/24
DHCPServer=on

[DHCPServer]
EmitDNS=no
EmitRouter=no
EmitTimezone=no
MaxLeaseTimeSec=20min
PoolSize=1

usb1.network

[Match]
Name=usb1

[Link]
RequiredForOnline=no
#MACAddress=

[Network]
DHCP=no
Address=192.168.6.2/24
DHCPServer=on

[DHCPServer]
EmitDNS=no
EmitRouter=no
EmitTimezone=no
MaxLeaseTimeSec=20min
PoolSize=1

wlan0.network

[Match]
Name=wlan0
Type=wlan

[Link]
RequiredForOnline=no

[Network]
DHCP=ipv4

wpa_supplicant-wlan0.conf

ctrl_interface=DIR=/run/wpa_supplicant GROUP=netdev
update_config=0
country=US

network={
    ssid="BeagleBone"
    psk="BeagleBone"
}