Linux 6.4 is set to remove the old CONFIG_SYSFS_DEPRECATED and CONFIG_SYSFS_DEPRECATED_V2 options that are used for running newer versions of the Linux kernel with very old Linux distributions and user-space tools. Pre 2007~2008 distributions as a result would likely run into trouble trying to run on Linux 6.4+ kernels.
These options that are finishing being cleared out allow for enabling deprecated sysfs features for supporting old user-space tools like udev. One of the last deprecated workarounds remaining by this option is for having block devices appear in the old /sys/block location rather than /sys/class/block.
Around 2006 is when user-space tools such as udev began seeing updates for the modern sysfs block location and work fine with newer kernels. Pre-2006 distributions not relying on udev are likely to be fine still too. But for those wanting to run a modern Linux kernel on the likes of Fedora Core 3, those days are numbered.
This patch by Greg Kroah-Hartman in driver-core-next drops the CONFIG_SYSFS_DEPRECATED / CONFIG_SYSFS_DEPRECATED_V2 options ahead of the Linux 6.4 cycle. Again this change should only affect nearly two decade old Linux distributions that have long been end-of-life. Building a modern kernel on those Linux distributions in recent years would likely have already proved challenging due to heightened Linux kernel compiler requirements and other factors.