The competition to become Real Madrid's main goalkeeper in my opinion is not the most interesting thing to discuss repeatedly, of course, because in my opinion we already know the difference in the qualities of the two goalkeepers.
For me, it is also interesting to discuss, why not?
Although Kepa may have more experience and most people assume he has a better quality, we don't know how Ancelotti thinks about it. So far, Ancelotti prefers Lunin to replace the position left by Courtois. I assume Ancelotti has a big reason to put Lunin as the main GK now.
Ancelotti borrowed Kepa from Chelsea to become the main goalkeeper due to Courtois' injury. Meanwhile, Lunin, who incidentally is Real Madrid's second goalkeeper, will still be Ancelotti's second choice, unless Kepa has performed poorly in a number of matches. Kepa Arrizabalaga is one of the good goalkeepers so far in Europe, but I don't think Lunin has been on the same level as Kepa.
I don't know if Ancelotti ever stated that he borrowed Kepa to be the main GK of Real Madrid. But surely Ancelotti needs a new GK because Real Madrid only has 1 GK left (Lunin). If there is something wrong to happen with Lunin (injured), Real Madrid will have no option for GK if they didn't have a new GK. Since Kepa seems to have a good quality, Ancelotti borrowed him from Chelsea.