Genexis EX600 - factory OpenWRT with everything blocked

My ISP gave me a Genexis EX600 router/base station in fiber installation ( It seems to be included in the package. The device clearly has some version of OpenWRT (or actually IOWRT, in it. Unfortunately everything is blocked - no real admin access - the user account cannot use ssh - very limited set of settings available. I was hoping I could transform this to a dumb AP with OpenWRT, but it seems to be impossible. For example, DHCP cannot be switched off.
I have not found any discussion on this device. Has anyone succeeded to put real OpenWRT to it?

IOWRT is only nominally "open source". It's a closed ecosystem for devices like yours. They didn't want to have to pay to develop an OS, and they didn't want it open, so they lifted OpenWrt and modified it to close it off. Things like this make me wish the Linux community had moved to GPL version 3.

I suspect you're right out of luck.