I spent some time trying to get this to work as expected, reading documentation and experimenting. I then searched and found this topic. I appreciate that github developers have constraints on their effort so may not implement every feature request promptly but this is continuing to confuse and frustrate users. May I make a request that, until this feature be implemented, the documentation be updated to describe the workflow more clearly. I like many others believed that new issues created in linked repositories would be added to the project via the configured automation. It would be a fairly simple and fast task to update the documentation to explain that this does not happen.
Further, one may consider the “Add cards” view as the triage view (in lieu of automation not working as expected), i.e. one may filter the “Add cards” to show issues from linked repositories which are not yet added to the project. This makes the “Add cards” list the equivillent to the triage list, i.e. everything reported that is not yet tasked. This was not evident until at least one reprository was added to the project so may also need to be documented.
(Using the “Add cards” list for triage would be more intuitive if it could be moved to the left side (for left to right users).)