Thanks, Oliver.
We booked DUB-ADD-CPT return for €1,200 each with both flights on 787s.
I didn't post a direct link as it seems we got the last 2 seats on one leg. i searched at skyscanner.net and ITA Matrix and found the fares. Unfortunately OTAs didn't pick up the ET flights so I booked on the (rather wobbly) ET website
https://www.ethiopianairlines.com/AA/EN/ .
Beware of Google searches. The first 3 items are adware, suspicious in my view. I wouldn't use ethiopiannairlines.com, ethiopiansairliness.co.uk or ethiopianairline.uk/ethiopian/airlines just in case.