Linus Torvalds has released Linux kernel 5.9, saying that he had hoped for fewer changes in this most recent cycle, but “at the same time there doesn't really seem to be anything particularly scary in here.”
According to Torvalds, the bulk of the changes are the networking fixes that he previously mentioned as pending in the rc8 release notes. In fact, he says “about half the patch (and probably more of the number of commits) is from the networking stuff (both drivers and elsewhere).”
Sarvottam Kumar reports for FOSSbytes that kernel 5.9 includes improved support for USB4 as well as file systems like Btrfs and F2FS, and it has boosted performance for both Intel and AMD systems. Furthermore, Kumar says, “since not many people use floppies for booting nowadays, it has also dropped support for multiple floppies.”
You can find a detailed list of Linux kernel 5.9 changes at Kernel Newbies.