Believe it or not, despite Nintendo phasing out features and services on the 3DS, they are still releasing some firmware updates for the handheld. Not often at all and never significant in terms of what they do. Still, Nintendo was releasing them.
For example, Nintendo did the same thing earlier tonight. If you’re still playing on your 3DS and want to download the update, it will set your handheld’s firmware to version 1.17.0-50U. As for the patch notes, they are not surprising at all. The only thing Nintendo mentions is that “further improvements have been made to overall system stability and other minor adjustments to improve the user experience.”