Thanks for your message. The connection between the two (i.e., "... and ...") was meant to emphasize that IPv6 is apparently not an option.
Starting from the very beginning (i.e., when OpenWrt is first installed), do I need to delete the WAN6 interface (by default, there seems to be WAN and WAN6), or just leave it alone and set "Obtain IPv6-Address" to Disabled?
My general understanding of this is limited, but I thought the very first exchange is PADI/PADO, e.g.:
From this, I assume that "Timeout waiting for PADO packets” means the very first step is failing, before the exchange of username/password, etc., as something about the PADI wasn't acceptable(?) to the ISP. Is that what this timeout indicates?
The Nexx WT3020 router's factory software worked to connect to the ISP, albeit jankily (before we reflashed it to OpenWrt), and a Mac (normally behind the router) can itself connect to the ISP via PPPoE (i.e., connecting the Mac directly to the optical modem, bypassing the router entirely), so I am guessing(?) the ISP isn't expecting a specific MAC address. As for a specific VLAN, I'm not sure how that would be specified, but I gather it's not necessary to provide a service name in the PADI.
Beyond that, is there some guide to troubleshoot the failure to get a WAN connection with OpenWrt?