USB Antenna Not Working on Dell Optiplex 760 Desktop?

Question

I have an issue very similar to (Ubuntu 17.10 Drivers Not Found/Working Properly?), but this was done on a fresh install of Kubuntu 18.04. This desktop doesn't have an internal Wi-Fi card and I'm currently using an old wi-fi module to get an internet connection there. The main issue with the old wi-fi dongle is that it doesn't have the proper antenna to provide adequate wi-fi connectivity, as this desktop is in a remote location where ethernet cords cannot easily reach, and where wi-fi signals are faint at best.

I used the new wi-fi antenna, which is the source of the trouble, first, and folowed the steps layed out in (Ubuntu 17.10 Drivers Not Found/Working Properly?) to try and get it to work. It didn't.

I made sure to not have the old wi-fi antenna in the USB slot while I was following the commands and only re-inserted it after completing all command and restarting the system and realizing that the steps were unsuccessful in being able to restore the USB antenna-driver functionality.

The New USB Antenna is the exact same as the one listed in (Ubuntu 17.10 Drivers Not Found/Working Properly?)

Edit 0: sudo dkms status yields

rtl8812au, 4.2.2: added 
rtl8812AU, 5: added

**Edit **: Output of lsusb (With Both USB Antennae in the USB ports)

Bus 002 Device 005: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter
Bus 002 Device 002: ID 0bda:a811 Realtek Semiconductor Corp. 
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 003: ID 0461:4d22 Primax Electronics, Ltd 
Bus 008 Device 002: ID 413c:2106 Dell Computer Corp. Dell QuietKey Keyboard
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

Edit 1: Modprobe Info & Secure Boot

sarah@SciLabComp0:~$ sudo modprobe 8812au
modprobe: ERROR: could not insert '8812au': Exec format error
sarah@SciLabComp0:~$ modinfo 8812au | grep A811
alias:          usb:v7392pA811d*dc*dsc*dp*ic*isc*ip*in*

Mokutil (The recommended way to check if secure boot is enabled based on another ask ubuntu question):

sarah@SciLabComp0:~$ mokutil --sb-state
EFI variables are not supported on this system

Solution

I have the 4.2.2 package downloaded on my 18.04 system. It will not 'make' without errors. I feel confident that you then tried the 5 version instead and it also didn't build properly for the same reasons. Let's clean them out:

sudo dkms remove rtl8812au/5.2.9 --all
sudo rm /usr/src/rtl8812au-5.2.9
sudo dkms remove rtl8812au/4.2.2 --all
sudo rm /usr/src/rtl8812au-4.2.2

There is an rtl8812au-dkms package available in the official Ubuntu repositories. It installs without error for me in 18.04. I suggest that you try:

sudo apt install rtl8812au-dkms

Reboot.

EDIT: We see from your modinfo that the installed version doesn’t actually cover your 0bda:a811 device. Let’s remove it and try a different driver file:

sudo apt purge rtl8812au-dkms
sudo apt install git
git clone https://github.com/abperiasamy/rtl8812AU_8821AU_linux.git
cd rtl8812AU_8821AU_linux
sudo make -f Makefile.dkms install
sudo modprobe rtl8812au

This driver clearly covers your device:

modinfo rtl8812au | grep A811

alias:          usb:v0BDApA811d*dc*dsc*dp*ic*isc*ip*in*
alias:          usb:v0BDApA811d*dc*dsc*dp*ic*isc*ip*in*
alias:          usb:v7392pA811d*dc*dsc*dp*ic*isc*ip*in*

You should be all set.

Comments

[Sarah Szabo]

It didn't work after reboot. New sudo dkms status says rtl8812au, 4.3.8.12175.20140902+dfsg, 4.15.0-22-generic, x86_64: installed rtl8812au, 4.3.8.12175.20140902+dfsg, 4.15.0-23-generic, x86_64: installed

[chili555]

Looks perfect so far. Please edit your question to show: lsusb with the antenna plugged in, of course.

[Sarah Szabo]

Post Updated. I left the working USB inserted when I executed the lsusb command, is that ok?

[chili555]

Just fine. May we now see: sudo modprobe 8812au and also: modinfo 8812au | grep A811 ??Secure Boot??

[chili555]

Exec format error; yikes! I will attack this later on tomorrow.

[Sarah Szabo]

I'm just happy that someone who knows what they're doing is able to help me. These device issues are beyond my current level of understanding.

[chili555]

Thanks for the kind words. Please see my edit above in a few minutes.

[Sarah Szabo]

Worked wihtou a problem after restarting. Thank goodness, no more .5 MB/s connection! Would upvote twice if I could!