Installing OpenWRT on RB2011UiAS-RM

Hello

I have a problem with instaling openwrt on RB2011UiAS-RM. I looked for documentation on https://openwrt.org/toh/mikrotik/rb2011 and https://openwrt.org/toh/mikrotik/common and search on google etc. but nothing helped.

I boot openwt over network without problem. Copy an openwrt upgrade fimware (http://downloads.openwrt.org/releases/19.07.8/targets/ar71xx/mikrotik/openwrt-19.07.8-ar71xx-mikrotik-nand-large-squashfs-sysupgrade.bin) to /tmp and run sysupgrade command. The device immediately reboots and boots RouterOS. Then I formatted nand in boot menu and after sysupgrade command device reports "kernel not found".

There are some errors after running sysupgrade command:

root@OpenWrt:/# sysupgrade -v -n /tmp/openwrt-19.07.8-ar71xx-mikrotik-nand-large
-squashfs-sysupgrade.bin 
Image metadata not found
Commencing upgrade. Closing all shell sessions.
Watchdog handover: fd=3
- watchdog -
killall: telnetd: no process killed
Sending TERM to remaining processes ... netifd odhcpd uhttpd ntpd ubusd urngd logd rpcd dnsmasq 
Sending KILL to remaining processes ... ntpd 
Performing system upgrade...
cannot find ubi mtd partition rootfs
libubi: error!: "/dev/" is not a character device
ubiupdatevol: error!: error while probing "/dev/"
              error 22 (Invalid argument)
tar: write error: Broken pipe
libubi: error!: "/dev/" is not a character device
ubiupdatevol: error!: error while probing "/dev/"
              error 22 (Invalid argument)
tar: write error: Broken pipe
sysupgrade successful
umount: can't unmount /dev: Resource busy
umount: can't unmount /tmp: Resource busy
umount: can't unmount /: Invalid argument
[   73.064433] reboot: Restarting system

Can anyone help me, please, what I am doing wrong?