The planned changes are coming in two stages. Initially, the imminent Fedora 36 release will remove the old fbdev driver, leaving only DRM and KMS. Then for Fedora 37, which is due later this year, it's proposed that the driver be removed from the X.org server as well.

The kernel's fbdev device has been deprecated since 2015. It's a very old-fashioned mechanism for the kernel to display graphics on the system console, which was introduced in kernel 2.1.109 back in 1999.

A visible use was the Tux logo that some distros display with the kernel messages during startup. It did have other uses, though, such as the ability to display software-defined fonts on the console, handy for those who use characters, or entire alphabets, not covered by the PC's character set. Last century, it was also used on some computers that don't have a native text mode, such as early Macintosh models.
Out of the frame

The functionality is not disappearing. What is going is the software and drivers that enable the kernel to do this directly. They will be replaced by a new driver called simpledrm, which emulates the old framebuffer. It sets up the display using KMS, which all distros have used for many years.