Gave it a shot (1472) but no luck.

Any suggestions on what to try?

Good question.

LAN device(s) pointed to WAN IP. LAN devices pointed to LAN IPs resolve fine and display webserver content. Cellphone (no WiFi) pointed to WAN IP does not exhibit the appended Opnsense webui port behavior.

I’m not sure what you’re suggesting but I am confident that IP Passthrough was set to DHCP Fixed on the BGW320-505 with the MAC of the Opnsense NIC before and after the Opnsense upgrade, if that helps.

So I’ve tried spinning up new turnkey containers for nginx to eliminate this as a potential issue. Everything can be accessed internally but new or old config alike, it’s the same inaccessible from WAN issue.