I didn't start from scratch from that tutorial, but I did find it helpful to finish things up and stabilize.
Your posting and its followup replies [Solved] How do i make a router with gateway was one of the first I attempted to follow, and I learned a good deal from it. But in the end, I couldn't get my Pi-3B+ configured for OpenWRT to work as a Ethernet-WAN, WiFi-LAN.
I did at least a dozen from-scratch installs using various tutorials or threads before I got a stable working system. You seem to have a good deal of experience with these. How about writing a tutorial that sets up Ethernet-WAN, WiFi-LAN using just the GUI as one of the simplest use cases, then add branches for various other use cases? If I had more experience, I'd try.