The iconic Mac startup chime is brought back by Apple in macOS Big Sur. The company suggested that it could come back very prominently by chime during yesterday's Worldwide Developers Conference, and people who have installed the first beta of Big Sur developers said it is back.
At the beginning of this post you can see a Mac on Big Sur playing the chime.
In 2016 the new MacBook Pros had been released for the first time, and since then, Mac (with the exception of the Macbook Air in 2017, the 13-inch version of the new MacBook) had not played the chime when it turned on.