RPi 4 doesn't bring up wlan1

Question

I have a Raspberry Pi 4 with Raspbian 10 (buster) installed. This device will be placed in a waterproof metal box which will limit the on-board wifi range. So, I want to use a USB wifi adapter with an external antenna.

I have configured the on-board wifi adapter to connect to my wifi router successfully. ifconfig returns the following

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
    inet 192.168.1.10  netmask 255.255.255.0  broadcast 192.168.1.255
    inet6 fe80::512c:3a96:6ee9:d7c3  prefixlen 64  scopeid 0x20<link>
    ether dc:a6:32:1a:79:93  txqueuelen 1000  (Ethernet)
    RX packets 124  bytes 12486 (12.1 KiB)
    RX errors 0  dropped 0  overruns 0  frame 0
    TX packets 136  bytes 16805 (16.4 KiB)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

My /etc/dhcpcd.conf file contains the following:

interface wlan0
    inform 192.168.1.10
    static routers=192.168.1.1
    static domain_name_servers=8.8.8.8
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
    metric 100;

interface wlan1
    inform 192.168.1.3
    static routers=192.168.1.1
    static domain_name_servers=8.8.8.8
    metric 200;
    wpa-conf /etc/wpa_supplicant/wpa_supplicant_wlan1.conf

My /etc/wpa_supplicant/wpa_supplicant.conf file contains:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
    update_config=1
    country=US

network={
        ssid="MYWIFI"
        psk="password"
        key_mgmt=WPA-PSK
}

and the second wpa_supplicant.conf file contains the credentials for the same network with a different IP. However, when I do an ifconfig command wlan1 never shows up.

The antenna I have is ASUS USB-AC56 which uses the Realtek RTL8812AU chipset. When I plug it into a USB port and run lsusb I get the following:

Bus 001 Device 004: ID 0b05:17d2 ASUSTek Computer, Inc. USB-AC56 802.11a/b/g/n/ac Wireless Adapter [Realtek RTL8812AU]

So the Pi sees the USB wifi adapter, but it doesn't bring up wlan1. What am I missing here?

EDIT to add the output of ip -all link show

pi@raspberrypi:/boot $ ip -all link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
link/ether dc:a6:32:1a:79:92 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state         UP mode DORMANT group default qlen 1000
link/ether dc:a6:32:1a:79:93 brd ff:ff:ff:ff:ff:ff

Answer 1

Thanks to @Ingo I got on the right path to finding my problem. I was not gettting a wlan1 because the correct driver was not installed. For the ASUS USB AC-56 I needed the Realtek RTL8812AU drivers installed.

From this thread, I was able to get the driver installed. Looks like @MrEngman's website has changed a little.

sudo wget http://fars-robotics.net/install-wifi -O /usr/bin/install-wifi

should be

sudo wget http://downloads.fars-robotics.net/wifi-drivers/install-wifi -O /usr/bin/install-wifi

the rest of his instructions work as documented

sudo chmod +x /usr/bin/install-wifi
sudo /usr/bin/install-wifiinstall-wifi -h # display help
sudo /usr/bin/install-wifiinstall-wifi -c # check to see if a driver exists
sudo /usr/bin/install-wifi # run the installer
sudo reboot

Now when I run ifconfig, wlan1 shows up as expected.