I am playing Wish in a Lurrus BO1 deck, Lurrus companion allows for permanents with CMC > 3 in the sideboard.
I have 6 more cards in my sideboard with Lurrus, so it should be possible to play any card from the sideboard with Wish.
If I have any permanent with CMC > 3 in the sideboard I cannot play any card, I cast Wish, sideboard cards are shown without the scroll bar at the bottom, battlefield does not get dark and I cannot select any card to play.
No issues if all cards in the sideboard respect Lurrus companion condition.