Canon PIXMA MG6620 on Linux Ubuntu
Open a terminal
sudo apt-get update
sudo apt-get install cups libxml2 libglade2-0 libpng1* libtiff*

Download the driver.
I had to use the Canon India link, as the Canon USA link did not have the Linux drivers. I also had to use the MG6670 model instead of MG6620, as the MG6620 was not listed.
https://in.canon/en/support/PIXMA%20MG6670/model
I downloaded the following printer driver:
IJ Printer Driver Ver. 5.00 for Linux (debian Packagearchive)
This software is a printer driver for printing using the Canon IJ printer.
Last Updated: 09 Sep 2014
Size: 474 KB

Extract the file: cnijfilter2-5.00-1-deb.tar.gz
Go to the downloaded file directory and extract the file:
tar -xvzf cnijfilter2-5.00-1-deb.tar.gz
cd into the cnijfilter2-5.00-1-deb directory and execute the install.sh
sudo ./install.sh

After the driver install, I went to Printers and the MG6600LAN as listed.

I did a test print of a Web page and the printers listed were Canon_MG6600_series, MG6600LAN and PDF to print from. I tried the MG6600LAN and the printed page was not clear, as though the driver was missing. When I chose the Canon_MG6600_Series, the printed page was clear.

Worked well.

I also download the scanner driver:
ScanGear MP Ver. 3.00 for Linux (debian Packagearchive)

This is a scanner driver for your selected model.
Last Updated: 09 Sep 2014
Size: 236 KB

I followed basically the same procedure for installing the scanner driver. But, when I ran the installation, the installation errored out, stating the driver was already installed. So I do not know if the scanner driver is part of the printer driver or Ubuntu has a default driver that recognized the MG6620 scanner. I ran the scanner program, and the scanner program recognized the MG6620 as “Canon PIXMA MG600 Series.” I did a test scan and was successful. The ouput of the scan is PDF.

FYI: My installation was done with the printer being wireless. The test printing and scanning was all done via wireless as well.

I am using Ubuntu 22.04. I have the default snap Firefox installed. When I download the external file (net.downloadhelper.coapp-1.6.3-1_amd64.deb) and do the installation, Video DownloadHelper does not recognize that the assisting file has been installed. After several hours of searching and reading, I finally found the solution from https://github.com/aclap-dev/vdhcoapp. I went to the following section:

Ubuntu Firefox: missed prompt

On Ubuntu, Firefox should have showed you a prompt to allow the coapp to communicate with the extension. Some people miss the prompt, or the prompt just never shows up.

There’s no user interface to change that setting. To solve this, run these commands (even if you don’t use Flatpak):

sudo apt-get install -y flatpak

flatpak permission-set webextensions net.downloadhelper.coapp snap.firefox yes

Ran: sudo apt-get install -y flatpak
The output:
Reading package lists… Done
Building dependency tree… Done
Reading state information… Done
flatpak is already the newest version (1.12.7-1).
flatpak set to manually installed.

Ran: flatpak permission-set webextensions net.downloadhelper.coapp snap.firefox yes
The output: Returns to the prompt.

I did not close Firefox or restart Firefox. I clicked on the Video DownloadHelper, clicked on the gear and then in the General tab clicked on the Recheck button. The page refreshed with the following results:
Found companion app: VdhCoApp 1.6.3
Companion app binary: /opt/net.downloadhelper.coapp/bin/net.downloadhelper.coapp-linux-64

Before I found the solution, these were the steps I took

Once the Video DownloadHelper plugin was installed, I tried to download a video. Video DownloadHelper prompted that a companion was required to continue with the download:

I downloaded the .deb package:

Once downloaded, I double clicked on the deb package and went through the installation. Once the installation was completed, I clicked on the Video DownloadHelper icon and clicked on the gear to get into the settings/configuration:

The following was shoing in the Companion App not installed: “Checking companion app returned: An unexpected error occurred.”

I then ran the following:
sudo apt-get install -y flatpak
flatpak permission-set webextensions net.downloadhelper.coapp snap.firefox yes

I did not restart Firefox, just went to the configuration of Video DownloadHelper and clicked on the “Reload” button, when the page refreshed:

Update 01/02/2024
I followed the same installation as above on a different computer and the install was unsuccessful. I did the follwing and the installation was successful. These instructons are on the DownloadHelper website: https://www.downloadhelper.net/install-coapp-v2

Since I am the only user on my computer, I used the “tarbz2 user-wide install.”

Linux x86/64bits tarball package

vdhcoapp-2.0.10-linux-x86_64.tar.bz2
Linux tarbz2 installation
tarbz2 user-wide install
# tar xf vdhcoapp-2.0.10-linux-x86_64.tar.bz2 -C ~
# ~/vdhcoapp-2.0.10/vdhcoapp install

Update 02/03/2024
Updated to vdhcoapp-2.0.10-linux-x86_64.deb and the plugin was not displaying as being installed.
I followed the instructions at : https://github.com/aclap-dev/video-downloadhelper/wiki/CoApp-not-recognized for Linux and followed the instruction:
Run /opt/vdhcoapp/vdhcoapp install (not as root! Don’t use sudo) to re-register the app.

$ /opt/vdhcoapp/vdhcoapp install
Installing…
Flatpak is installed. Making the coapp available from browser sandboxes:
Linked coapp within org.mozilla.firefox.
Linked coapp within com.brave.Browser.
Linked coapp within com.google.Chrome.
Linked coapp within com.google.ChromeDev.
Linked coapp within org.chromium.Chromium.
Linked coapp within com.github.Eloston.UngoogledChromium.
Linked coapp within com.microsoft.Edge.
Linked coapp within com.microsoft.EdgeDev.
Writing /home/blogger/.mozilla/native-messaging-hosts/net.downloadhelper.coapp.json
Writing /home/blogger/.var/app/org.mozilla.firefox/.mozilla/native-messaging-hosts/net.downloadhelper.coapp.json
VdhCoApp : VdhCoApp is ready to be used

The instructions from the site:

Linux (all)

• Run /opt/vdhcoapp/vdhcoapp install (not as root! Don’t use sudo) to re-register the app.
• Move to the installation folder of the coapp in your terminal, and run: /opt/vdhcoapp/vdhcoapp –info. It will run some diagnostic operations.
• do not install vdhcoapp within the /usr/ directory, it won’t be detected by your browser. See here why.

Update 05/27/2024
Another update!

Ran the following, as suggested by the app:
$ curl -sSLf https://github.com/aclap-dev/vdhcoapp/releases/latest/download/install.sh | bash
Downloading: https://github.com/aclap-dev/vdhcoapp/releases/latest/download/vdhcoapp-linux-x86_64.tar.bz2

Results:
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 –:–:– –:–:– –:–:– 0
0 0 0 0 0 0 0 0 –:–:– –:–:– –:–:– 0
100 52.8M 100 52.8M 0 0 41.1M 0 0:00:01 0:00:01 –:–:– 66.8M
Extracting tarball…
/tmp/vdhcoapp-ZBXbtG: bzip2 compressed data, block size = 900k
Registering CoApp
Installing…
Flatpak is installed. Making the coapp available from browser sandboxes:
Linked coapp within org.mozilla.firefox.
Linked coapp within com.brave.Browser.
Linked coapp within com.google.Chrome.
Linked coapp within com.google.ChromeDev.
Linked coapp within org.chromium.Chromium.
Linked coapp within com.github.Eloston.UngoogledChromium.
Linked coapp within com.microsoft.Edge.
Linked coapp within com.microsoft.EdgeDev.
Writing /home/blogger/.mozilla/native-messaging-hosts/net.downloadhelper.coapp.json
Writing /home/blogger/.var/app/org.mozilla.firefox/.mozilla/native-messaging-hosts/net.downloadhelper.coapp.json
Writing /home/blogger/.config/google-chrome/NativeMessagingHosts/net.downloadhelper.coapp.json
VdhCoApp : VdhCoApp is ready to be used
CoApp successfuly installed under ‘~/.local/share/vdhcoapp’.
To uninstall, run ‘~/.local/share/vdhcoapp/vdhcoapp uninstall’ and remove ‘~/.local/share/vdhcoapp’.
Re-run that script to update the coapp.