The router was flashed with 19.07 OpenWRT.
After setting up WAN connection to my ISP via PPPoE I try to update packages. I opened web interface and went to SYSTEM->SOFTWARE, and Free Space meter bar was in UNKNOWN state.
Rebooting doesnt help, so I decided to reflash it.
Now it shows free space properly, but I found new trouble - no WIRELESS folder in NETWORK.
When I setting up WAN connection via DHCP the router works good. Memory tested OK, WIRELESS folder is on its place.
I changed router to another EA3500 and got same troubles. The firmware is from [https://openwrt.org/]
My biggest trouble that port forwarding doesnt work with PPPoE WAN connection, via DHCP all is OK.