The 5.5 kernel was released on
January 26. Over the course of this development cycle, it was
occasionally said that the holidays were slowing contributions. At the
end, though, 5.5 saw the merging of 14,350 non-merge changesets from 1,885
developers — not exactly a slow-moving cycle. Indeed, 5.5 just barely
edged out 5.4 as the kernel with the most developers ever. Read on for our
traditional look at where the contributions to 5.5 came from, along with a
digression into the stable-update process.

Source: LWN.net – [$] Some 5.5 kernel development statistics