You thought the Nintendo Switch was supposed to get its 6.0.0 update today, but it looks like the Nintendo Wii U did instead. The retired console got a new firmware revision, the first since July 2017. By now, you should know the drill; this is a stability update. Chances are, Nintendo is trying to prevent any further exploits, and only time will tell if they were successful.
Improvements to system stability and usability:
Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience