It's not included. There's no discount either.

The Wightlink ferry between Portsmouth Harbour and Ryde Pier Head is FREE for pass holders and can be added in the journey planner alone or as part of a journey to any Island Line station (Shanklin for example). Journey time is 22 minutes and the frequency is normally hourly.

Wightlink themselves say Interrail is not valid:

https://www.wightlink.co.uk/plan-your-journey/routes/portsmouth-ryde-route

​@Eurail Community Moderator this means the app should be corrected: the ferry between Ryde Pier Head and Portsmouth Harbour is not in the pass network.

Hi ​@rvdborgt, we’ve now reported the clarification regarding the ferry between Portsmouth Harbour and Ryde Pier Head. We will send the update on this post after receiving the details.

Thank you for bringing this to our attention!

Hi ​@rvdborgt, our product team has confirmed that the ferry is not valid for Pass holders. We received this clarification from RDG that the GWR and SWR teams have double-checked that these routes are not available to Eurail/Interrail Pass holders. The timetable is going to be adjusted to reflect this update

Hi everyone,

The timetable team has corrected the route between Ryde Pier Head and Portsmouth Harbour, which is not valid in the Pass network. This update is now reflected correctly in our app (using the live timetable) and on the reservation page.

Have a nice day!