Rock PI 4B+ uSD card to eMMC switch

Hi after a few days of testing with my Rockpi 4b plus v.1.73 and latest 5.10 kernel I found the solution to work SD card or the 16Gb eMMC on board.
The problems arose after writing the emmc on the block ‘/ dev / mmcblk2’, working later on the SD card, at boot I alternated once emmc and once sd card.
After an update & upgrade, and after setting the static IP via NetworkManager, it was no longer possible to access it on SD or on emmc, as I had transferred the content to the latter.
Rewritten the SD card several times and repeated the procedures again it was blocked, useless to follow the instructions for the SPI boot in which they say to put the jumper between PIN 23 and 25.
Finally I checked the hw_intfc.conf file where I have all commented on right now.
Then in the extlinux.conf file I cleared the startup check and this is how it is now:

timeout 10

label kernel-5.10.131-2-rockchip-g8802564cbf09
kernel /vmlinuz-5.10.131-2-rockchip-g8802564cbf09
initrd /initrd.img-5.10.131-2-rockchip-g8802564cbf09
devicetreedir /dtbs/5.10.131-2-rockchip-g8802564cbf09
append earlyprintk rw init = / sbin / init rootfstype = ext4 rootwait root = UUID = 4ceb5527-58bb-459e-973b-c8bbb1dcfc2e

By modifying this boot file I am now able to boot either from SD card or emmc simply by holding or removing the jumper between pin 23 and 25 and then reboot.
I think it’s all due to the check that it no longer does at boot with this line removed: ‘menu title select kernel’

I don’t know if anyone can help, as the kernel is new and there is no instruction manual.