Rockstar recently released 39 new screenshots for GTA VI, featuring a character who appears to be American rapper Kodak Black. IGN suggests that he will appear in the game as a non-player character (NPC). These official assets were released about two weeks before the game's launch.
Zooming in on the screenshot reveals that the character is holding a cup with the "Jack of Hearts" logo. Jack of Hearts is a club in GTA VI that has already appeared in multiple promotional materials.
Travis Scott also directly mentioned this club in his song "RHYNO," which was produced specifically for the GTA VI soundtrack. The screenshots thus provide specific visual clues linking Kodak Black's likeness to Jack of Hearts.
What can be confirmed is that Kodak Black's likeness appears in the official screenshots. It has not yet been disclosed whether his corresponding NPC will participate in missions, how many lines of dialogue he will have, or what role he will play in the story; the screenshots also do not provide evidence of other musicians actually appearing in the game.