No cursor on the framebuffer, and I checked the number of 0’s in vt.cur_defaut=0xF00058 about a dozen times; the mistake I made the first time was I only added two zeroes. And I was also slightly suspicious, because the filesystem interface only accepts decimal. Anyway, all of that before just noticing today that I spelled “default” with no “l”.
The cursor returns to the framebuffer if you fix the last part of /boot/extlinux/extlinux.conf so that it reads vt.cur_default=0xF00058. (That is from hyperyay in RO1 : No software cursor displayed on fbcon - #20 by hyperyay .)