I have a x86 machine that I will use as local router that will have WAN connection over USB dongle.
Now I installed OpenWRT on it and it designated it's only Ethernet port as lan and I can not access internet over it if I connect to a router. I also can not access luci or ping my x86 machine if I connect Ethernet cable to my laptop but that may be because I disabled DHCP.
To configure it can I just plug in USB NIC to a router or share wan over USB with internet tethering from smartphone as temp WAN access while I set it up? Or do I have to configure Ethernet port to do both lan and wan functions?
You'll need the drivers for your USB dongle... have you identified the chipset so you can install those?
You probably shouldn't disable DHCP on your lan interface, at least right now. In general, most use cases will have it enabled. However, if you have an alternate DHCP server and/or you don't want DHCP at all, sure, you can disable it. But while you're getting things working for the first time, it's best to have as close to a default install as you can.
I do not have a WAN connection on the x86 machine... I can not install any drivers I am not online.
Despite that I am getting some kernel noise about USB connection... no errors but no connection either I think I have to configure WAN connection manually for USB dongle or mobile phone tether to even have a chance of working.
The default build does not include any drivers for USB-Ethernet converters or mobile phone tethering.
The usual approach to this is to first set up OpenWrt as a LAN device then connect to a LAN and run opkg to install driver packages over the Internet. Or you can use the Image Builder or Firmware Selector to build a custom image that contains the drivers you need. Installing this image should detect the additional port and configure it as a WAN during the first boot.
Since you're using an x86 machine, you can also make the built-in ethernet port (assuming it's working) operate as the WAN port and then use an attached keyboard and display to install the drivers for the USB adapter.
you've got a total of 3 viable options for getting that ethernet adapter working... it just depends on which is easiest for you.
I also edited static IP to not conflict with my main routers IP
I also removed br-lan device from lan
2. I plugged in USB NIC downloaded drivers for it and switched it to be my wan router.