Tetris 99 may be 5 years old, but the game is still supported, even today. The game still hosts Maximus Cup events from time to time. However, Nintendo wasn’t really that interested in updating the game. In fact, it’s been almost 2 years since the last update.
Well, as of tonight, that has changed. Tetris 99 has been updated. After you update it should be on version 2.4.0. As for patch notes, there aren’t many. The only thing Nintendo mentions is that “various adjustments have been made to improve the gaming experience”.