Ok using Android Menu “update&backup” actually works. here is complete log over serial console.
From 1 - 230 line ist just clean u-boot boot and printenv part.
Line 256 show actually reboot mode which is “update” which should be same as doing in “u-boot” the “run update” @Gouwa can you confirm this?
[ 281.279063@0] reboot: Restarting system(init) with command 'update'
From Line 372 shows actually update and activating multiboot mode
reboot_mode=update
@balbes150 if you check old paste log from line 131 you will see this same file. Also this pastelog have printenv which was in that time there.
reading aml_autoscript
Any way I have now @balbes150 LibreELEC booting from microSD. Why it does not work with u-boot “run update” I am not quite sure, but maybe @Gouwa or someone else write this.
Thank you @balbes150 and @harpmaster for your time and instruction.