To avoid having to expose more of the host filesystem in the sandbox but still allowing extending Chromium, the following extension points are defined:

• com.github.Eloston.UngoogledChromium.Policy
• com.github.Eloston.UngoogledChromium.Extension
• com.github.Eloston.UngoogledChromium.NativeMessagingHost

This extension point can be used to configure custom Chromium policies and is currently on version '1' and will make any policy under the policies/managed and policies/recommended subdirectories available to Chromium.

Similarly to the above, but for Chromium extensions, this extension point is also currently on version '1' and will make any extension under the extensions subdirectory available to Chromium.

Also as above, but for native messaging host support. As the other extension points, this extension point is also currently on version '1' and exposes the native-messaging-hosts subdirectory to Chromium.

Extension points can be provided as regular flatpaks and an example is provided under examples/policies/block-dinosaur-game. Important to note that extension points' name must follow the syntax of <ExtensionPointName>.<id>, where <ExtensionPointName> is one of the supported extension points above and <id> is a generic id for this specific extension point.

Flatpak also supports “unmanaged extensions”, allowing loading extensions installed into /var/lib/flatpak/extension and $XDG_DATA_HOME/flatpak/extension. This can be useful for example to allow system administrators to expose system installed policies, extensions, etc.

One example of such "unmanaged extension" could be an extension point that exposes all system policies installed under /etc/chromium-browser/policies/{managed,recommended}. This could be done for example by creating an extension point under /var/lib/flatpak/extension/com.github.Eloston.UngoogledChromium.Policy.system-policies, with /var/lib/flatpak/extension/com.github.Eloston.UngoogledChromium.Policy.system-policies/<arch>/<version> being a symlink to /etc/chromium-browser. Note that <version> must match the extension point version.

Also important to note that in the example above one would not be able to symlink the actual policy file directly, as otherwise flatpak would not be able to resolve the symlink when bind mounting the extension point.

1. Download and execute widevine-install.sh
2. Restart the browser

For other problems please check https://ungoogled-software.github.io/ungoogled-chromium-wiki/faq before creating an issue in this repository. However keep in mind the following while reading any document about Ungoogled Chromium:

• ~/.config/chromium -> ~/.var/app/com.github.Eloston.UngoogledChromium/config/chromium

~/.config/chromium is not accessible to Ungoogled Chromium and the above path should be used instead.

Also keep in mind that after making a change, make sure to do a flatpak kill com.github.Eloston.UngoogledChromium to ensure that Ungoogled Chromium was actually restarted. This is because by default, Chromium runs in the background after being started for the first time (closing the window doesn't actually exit Chromium, just keeps it in a sort of "standby" mode).