https://www.hotukdeals.com/deals/champions-league-final-europa-league-final-free-live-on-bt-sports-youtube-channel-2939422I had a chat with BT live chat and the person I chatted with said both the champions league final and the Europa league final 2018 will both be streamed on YouTube.
There is currently no public post from BT sport confirming this but I will upload the chat.
Kick off date & times are:
Europa League Final 16/05/2018
Marseille vs Atletico Madrid KO 7.45pm UK time
Champions League Final 26/05/2018
Real Madrid vs Liverpool KO 7.45pm UK time
They showed the final for free last year too, so I don't see why they wouldn't now?