Not much has come out recently on this in terms of reports from the media outlets, his post is really the only news so far.
Would make me believe he will most likely try and avoid a third surgery and see if he is better after the summer. In terms of comparing him to Umtiti, when you look at the major factors here, I'd say they sorta wash and its hard to gauge or project anything in terms of how this could impact his career longterm. Ansu is lighter and seems very fit and physically, he might be able to recover and fully heal without the removal.
What worries me longterm however is his playing style. His explosion and agility in tight spaces is a key part of how he dribbles and beats defenders. If you go back and watch some his goals, a lot of them are quick, driven low shots with little to no backswing. Just from my little experience playing, you put a lot of the tension and power in your quads and knee and you explode through the ball. It is going to be really hard for him to do that shot on his left foot if he doesn't have his meniscus and let's assume the best and say he does recover without a 3rd operation, trusting his body to do that again is the hardest and longest part when he is on his way to trying to train again. That said, if he ends up removing the meniscus, all of this is why it could be more complicated than it was for Umtiti. The positional demands of a CB vs. a LW/SS are very different so the long-term effects of this route might catch up with Ansu faster than they did with Umtiti and that is my big concern if he does need the knife.
Best thing to do really is pray it heals with good PT and treatments. It'll be a win even if we have to wait to see him play until 22 if he can recover naturally. Konrad, Collado and Trincao can all chip in to fill his role in the meantime.
Wishing for the best for this kid!