Casper Ruud isn't particularly interested in tennis on grass as he opted to prepare for the event in Norway by playing on a court that has no grass whatsoever.
Ruud famously trended on tennis Twitter last year after he admitted that tennis should not be played on grass which is suited for golf instead. His results on grass so far have proven that he's really not that of a good player on it but he could possibly be solid on it in the future if he tries a bit more.
His game isn't suited for grass to be fair so that makes it a bit tougher. Even so, Ruud planned to play in Halle to prepare for the event but withdrew from the event just days ahead of its start. It was a curious move that made some wonder whether the fatigue from Paris was to blame for that and it might have been, but he's practising again.
Back home in Norway, Ruud stepped on a tennis court to stay in shape and prepare for Wimbledon however the court is not a grass court. Ruud is actually preparing in his home tennis club on hard courts which is a curious choice considering that they play very differently from clay courts. He is likely getting some early work in for the North American stretch in the second part of the summer but that might be a bit premature.
Either way, we won't see Ruud on the grass until he makes his way to Wimbledon which should happen in the coming weeks. His preparation choices have been sus in the past with the early part of this year proving why. We'll see if this decision ends up being some 4d chess move by Ruud or whether he really simply dislikes playing anything on grass other than golf.