The Skywalker Saga began with Anakin Skywalker, the Jedi who fell and became Darth Vader. While the sequel trilogy was the first to not specifically include some version of Anakin Skywalker as a character, outside of cameos, the character still casts a long shadow over the entire story. In Star Wars: The Force Awakens we see that Kylo Ren is in possession of Vader's melted helmet, as he tries to commune with it, and it appears that Star Wars: The Rise of Skywalker almost called back to that moment with a similar scene.
We do see Vader's helmet in Star Wars: The Rise of Skywalker. Ray comes across it while traversing the Star Destroyer, and it's the room she finds herself in when she and Kylo Ren have a Force connected lightsaber battle. However, images recently posted to Imgur show a scene with Kylo Ren alone with the helmet, possibly trying to connect to it as he had tried before.
With only a few still frames, it's impossible to know exactly what we're seeing. The only thing we can know for sure is that this scene would have taken place prior to the time Rey finds the helmet, as the pedestal the helmet is on is destroyed during the fight, and seeing it is what reveals Rey's location to him. Really, the most interesting thing about it is that the helmet being on the ship reveals that Kylo Ren literally brings the thing with him wherever he goes. Whatever ship he happens to be on, he finds a special place for it.
Between confirmed deleted scenes, and concept art there is a fair amount of Star Wars; The Rise of Skywalker that was once an idea, but didn't end up in the final version of the film. This, along with other rumors, have led to many believing there's a mysterious "J.J., Cut" of the film, a previous, significantly different, version, that is sitting in a vault somewhere never to see the light of day. While we know that some of these early ideas did survive simply the idea the phase, it's far from clear how much was actually filmed.
Every movie has ideas that don't make it past concept art or scenes that end up not being used. While Star Wars; The Rise of Skywalker may have had a lot of ideas that ended up not being used, this one looks like a simple scene that was just decided to be unnecessary. The Rise of Skywalker is a long enough movie as it is and there's, quite honestly, a lot of plot that the move barrels through in that time, you get the impression that anything that was filmed that didn't directly serve that plot had to be cut.