Hi all, I found where the problem was... My SD-card was not working correctly. My apologies. The system could not read/find ext4 partition on SD-card (because of "unknown" type and mounting point). I guess this happened when I erased my previous ext4 partitions by Windows disk manager and re-wrote Armbian image later. Problem was resolved as soon as I reformatted/recorded new image by Ubuntu. Thank you all.
Last Man's post in problems with booting from SD-card (initramfs) was marked as the answer