There is an opensense option that blocks rfc1918 traffic on the wan. your wan ip addeess range matches rfc1918. I do not remember where to disable it exactly, but this is the error.

I have no idea what you want to achieve.

All you need to do is add a static route to your fritzbox for 192.168.1.0/24 via 192.168.1.x, where x is the wan ip of the openwrt router and then add a firewall rule in openwrt to allow either all traffic or add specific rules/ports from wan to lan. Another way, if you only need ssh is setup portforwardimg im openwrt so that wan port tcp 22 is forqarded to 192.168.1.30 and then connect from 192.168.178.10 to the wan ip of the openwrt router, which will forward it.