I already build a lot of images for another boards. My problem is uboot spl corrected 1536mb ram okay, but after that, it load uboot and say dram 2gb 0gb effective. Real ram is 1,5gb

@Sancho perfect. I will try it out and will inform you later. I have also discovered that the power adaptors packed with the iSG Box are low quality and some of those can't even reach 1,5 A. Which can cause instability issues and failed HA updates, install, armbian crashes, etc.

this means bootloader in SPI-flash is used if armbian is booted from sd-card slot, the armbian bootloader from sd-card it used, at least that is what i think so you can wipe spi-flash or wriie a working bootloader in there

Then my guess was correct. That's the image I tested a few minutes ago. https://paste.armbian.com/enadozucir

This one Armbian_26.5.1_Orangepi5_trixie_vendor_6.1.115_minimal.img