The injury suffered by Courtois forced Ancelotti to play lunin in every game they played in the rest of the season, but for now Courtois has recovered and is ready to become Madrid main goalkeeper again, but I think it will actually give Ancelotti a dilemma at this time, in the rest of La Liga matches of course Ancelotti can play lunin and courtois alternately but the Champions League of course the right decision must be taken by Ancelotti
Courtois is a great goalkeeper from Atletico Madrid to Chelsea then Real Madrid, he always shown his great saving skills but it's unfair for Lunin if Ancelotti chose Courtois for the Champions League final match. Because throughout the season, Lunin contributes a lot and makes many great saves to bring Real Madrid to the final match. First, it's issue to respect Lunin.
Second issue if choosing Courtois, it's risky to pick a goalkeeper who missed most of the season and only returns recently, for a most important match of a season. I believe Ancelotti will pick Lunin for the match because of both reasons, respect for contributions of Lunin, and risk from Courtois' performance after his injury recovery.
Real Madrid is far ahead of Dortmund in terms of performance and confidence, so the chances of Real Madrid winning the final match are high. Another positive thing for Real Madrid is that Real Madrid has no injury problem which means all the players in their starting XI can play in the Champions League final for Real Madrid.
On paper, Real Madrid have many supporting factors to beat Dortmund in the final. In an actual match, not on paper, if Real Madrid players play as well as normally, they are able to beat Dortmund and one more Champions League trophy for their club.
Real Madrid have very deep squad but have no player injury before the final match looks to be a good information on player resource for Carlo Ancelotti.