The HP8720 printer successfully prints from Document Scanner, LibreOffice, and Firefox but fails to print documents or web pages from Chromium browser on Ubuntu. Typically, this issue arises due to Chromium-specific print settings, missing print drivers, or incorrect configuration. Follow the detailed steps below to troubleshoot and resolve the problem effectively.

Method 1: Reset Chromium Print Settings

Sometimes, Chromium browser retains incorrect or incompatible print settings that prevent proper communication with your printer. Resetting these settings often resolves printing issues.

Step 1: Open your Chromium browser and enter the following URL into the address bar:

chrome://settings/printing

Press Enter to access the printing settings page.

Step 2: Click on "Printers" and locate your HP8720 printer. Click on the three-dot menu next to it and select "Remove" to delete the existing printer configuration from Chromium.

Step 3: Restart Chromium completely. Close all browser windows, wait a few seconds, and then reopen the browser.

Step 4: Attempt to print again by pressing Ctrl + P to open the print dialog. Select your HP8720 printer from the dropdown menu. Chromium should automatically re-detect and configure the printer correctly.

Method 2: Reinstall or Update HP Printer Drivers

If resetting Chromium's print settings doesn't fix the issue, the problem might be related to outdated or improperly installed printer drivers. Reinstalling or updating the HP printer drivers ensures compatibility and correct functionality.

Step 1: Open a terminal window by pressing Ctrl + Alt + T. First, remove existing HPLIP drivers (if installed) by running:

sudo apt remove --purge hplip*

Confirm the action when prompted.

Step 2: Update your package database and install the latest HPLIP (HP Linux Imaging and Printing) package by executing:

sudo apt update
sudo apt install hplip hplip-gui

Step 3: After installation, run the HP setup tool to configure your HP8720 printer properly:

hp-setup

Follow the on-screen prompts carefully to complete the printer setup.

Step 4: Restart your computer once the setup is complete. After rebooting, launch Chromium and attempt printing again to verify the fix.

Method 3: Check and Adjust AppArmor Settings

In certain Ubuntu installations, AppArmor profiles may restrict Chromium's ability to communicate with printer services. Adjusting or temporarily disabling AppArmor profiles related to Chromium can resolve such printing issues.

Caution: Modifying AppArmor settings involves system security. Proceed carefully and revert any changes if unrelated issues occur.

Step 1: Open the terminal and temporarily disable the Chromium AppArmor profile by running:

sudo aa-complain /usr/lib/chromium-browser/chromium-browser

This command switches AppArmor to complain mode, allowing Chromium to operate freely while logging any conflicts.

Step 2: Restart Chromium and attempt printing again. If printing works, AppArmor was causing the issue.

Step 3: To permanently adjust AppArmor settings, you can edit the profile located at:

/etc/apparmor.d/usr.lib.chromium-browser.chromium-browser

Use a text editor like nano or vim to modify rules related to printing, or consider leaving AppArmor in complain mode if you prefer simplicity and understand the security implications.

Method 4: Use CUPS Web Interface to Reconfigure Printer

If the above methods fail, reconfiguring your printer through the CUPS (Common Unix Printing System) web interface can solve configuration mismatches between Chromium and your printer.

Step 1: Open a web browser (e.g., Firefox or Chromium) and navigate to the CUPS interface by entering:

http://localhost:631

Step 2: Select "Administration" from the top menu, then click "Manage Printers." Find your HP8720 printer in the list and click on it.

Step 3: Choose "Modify Printer" from the dropdown menu. When prompted, enter your system username and password to authenticate.

Step 4: Follow the steps provided by the wizard, ensuring the correct driver (HP8720 driver or recommended alternative) is selected. Complete the wizard and confirm the changes.

Step 5: Restart Chromium and try printing again to verify the fix.

After following these steps, your HP8720 printer should successfully print from Chromium on Ubuntu, matching its functionality in Document Scanner, LibreOffice, and Firefox. If issues persist, consider checking Ubuntu community forums or official HP support resources for further assistance.