This is the newest video on updating the firmware of the Shimano Di2 groupset.
The battery and the derailleurs are updated wirelessly using the Shimano e-tube app but the levers should be updated wired only, also using the Shimano e-tube app.
I hope this video helped you.
00:00 Wake up your Di2
00:11 Open the e-tube app - press the button
00:30 Check the updates and start the update wirelessly
01:04 How to update the levers (wired only)
01:53 The tools needed
02:28 The electrician's job
04:00 wired firmware update L
05:04 wired firmware update R
07:45 Last checks
08:00 Synchronized shifting enable
08:35 Last check