OK...but unsure why you don't wanna provide logs...
I hope you're not doing that because you believe there's some bug you convinced yourself of.
EDIT: I was gonna add, I'm not familiar in OpenVPN on OpenWrt specifically, it was my understanding the instructions properly set up this forwarding.
If not, I was simply gonna suggest re-configuring the firewall to add tun0 to its own firewall zone, and permit forwarding to/from LAN.