Ivan,

If you still get the raspberry icons, you might have done the same thing I did wrong the first time.
There is an important line on that page:
Remove other things
Still in “/boot/cmdline.txt”, add below at the end of the line
Make sure in cmdline.txt there are no linefeeds. In other words ...

Hello,

I'm facing the same issue. I made some progress that might help you a bit.

I followed the steps found on this site:
https://scribles.net/customizing-boot-up-screen-on-raspberry-pi/

All the boot text disappeared, except for two lines:
[ 0.000000] [Firmware Bug]: Bootloader left irq enabled ...