LibreELEC Legacy boot

Yes, I connected the hard drive to another PC and created for him the same thing I have done according to your instructions before the flash disk.

I do not know if it translates properly but I have already mentioned it several times:
Rufus flashdrive created using the Ubuntu ISO works. When creating, I'm asking that the ISO image can vytviřit as DD but recommended ISO.

-> Ubuntu LIVE boos USB -> Works on my laptop.

So I've done crazy:
I made flashdrive Syslinux and crossed the kernel. Once I quickly ran syslinux said flsah memory for a second that was made over LibreELEC creator and it works. Heureka: D

Thanks for your help, even though I was finally resolved in such a strange way.