Test plugin files:

These files will work for the activity plugin mod_ouwiki (available from https://moodle.org/plugins/mod_ouwiki), but should work for most activity plugins with a small amount of editing. These files should make the activity display one fixed page on the mobile app for that activity that includes an image. This is not exciting, but does demonstrate in a very simple manner the issue with core-external-content and the size context menu item.

First add mod_ouwiki files from the plugin store to a test site. (Alternatively please use whatever activity plugin that is not already set up for mobile app that you have available, but not a core activity of course.) Run site notifications. Check the activity is working as a normal website plugin. 

Next add these four files to the plugin and enable mobile app support (for full details please see https://docs.moodle.org/dev/Mobile_support_for_plugins).

mobile.php should be added to mod/ouwiki/db/
ouput-mobile.php should be added to mob/ouwiki/classes/output/ and renamed mobile.php (sorry for temporary name)
mobile_view.mustache will need to be added to mod/ouwiki/templates/
cat-ramiz-dedakovic-u4gwRbr2_j0-unsplash.jpg should be added to mod/ouwiki/tests/fixtures/

Alternatively you can unzip ... to the mod folder in your site (it has ouwiki with the files above ready to use). You will still need to run site notifications and turn on mobile app support on your site (if necessary).

Finally you will need to enroll a student on a course on your site and add an ouwiki activity to the course then purge caches.

Now in your desktop app (run ionic serve -b) open your site, navigate to the course, then open the ouwiki activity and check the test steps. You may need to delete your site from the desktop app and reload it a second time if the ouwiki does not open a simple page with a cat image (and or purge caches again).