On September 30, Nintendo released Switch Firmware 9.0.1 which is a minor update that comes with no new features except some bug fixes.
FW 9.0.1 is such a minor update that Atmosphere 0.9.4 works without any modification!

These fixes include:

  • A bug in which you’re asked to remove joycons during set-up on a Switch Lite has been addressed
    • The Switch Lite doesn’t have detachable joycons but the controls are part of the system itself

  • An issue in which errors might’ve been triggered during playing games has been fixed
    • This description is pretty vague as Nintendo didn’t specify exactly where the issue happened

    Unlike many other Switch firmware updates, FW 9.0.1 doesn’t break Atmosphere CFW compatibility which has been confirmed by SciresM and various individuals online. Furthermore, users have indicated that most homebrew including RetroArch, Tinfoil, Checkpoint and NX-Shell are working just fine on this firmware which goes on to show how inconsequential its changes are when it comes to hacking console.
    As of right now, there seems to be no definitive word as to whether sigpatches for FW 9.0.0 are compatibile with FW 9.0.1 but the general consensus is that they are since FW 9.0.1 didn’t change many files.