Ok perhaps I wasn't clear. Here's a better illustration:
ONT -> Pi (Ethernet cable from ONT going into TP-Link UE300 adapter on the Pi) -> This is my WAN
Pi -> PC (Ethernet cable from Pis Ethernet port to PCs ethernet port) -> This is my LAN
Seems like this is the most common setup I've seen people use. Just need to compile and install the drivers to get the USB to Ethernet adapter working.
Then the next would be to get the config right. Once those are done, I should have a working Pi router
the correct drivers for TP-Link UE300 is kmod-usb-net-rtl8152 and you don't need to compile, you just need to install that package using the method I suggested before - i.e. download the IPK on your computer, then upload it to the pi4 in the software page
Yup, I've installed it and the adapter is recognized in ifconfig now. Just need to configure the network file for internet access. I'm still getting a PPPoE error.
Check https://openwrt.org/docs/guide-user/network/wan/isp-configurations?s[]=pppoe
There are several pppoe settings for different countries and their ISP.
It could be that your provider need some more settings within you WAN config, like 'option mtu 1500'. 'option macaddr XX:XX:XX:XX:XX:XX' (to clone a mac) or 'option ipv6 auto'.
These are examples, I am not using pppoe so I can't tell exactly.
Your first WAN example has also the following in config:
I'm managing to get internet connection from the Pi itself. However, now I can't get any internet connection from the LAN PC.
From the logs, it tells me that PPPoE connects, and I can verify by sending pings to the internet from the Pi itself. However, the problem starts here:
With not a 'real' log it's almost impossible to see where your problem is (due to timing, where is the log from, etc.)
In your summary is stated:
(2) WAN is now up (Which eth is up?)
(4) eth0 link is up (ok)
(8) br-lan is up (ok)
(10) eth0 is down (weird, WHY?)
(14) eth1 link is down? (Where did eth1 went up before?)
Check your /etc/config/network file.
What device (old: ifname) is used for WAN?
What device (old: ifname) is used under br-lan?
My guess still (only) eth0 is used for LAN as well as WAN?
A defect cable could cause eth0 goes down (9-10) what else could cause this?
How much time is between message 9 and 10?