Tried to install Index of (root) / releases / 18.06.1 / targets / x86 / generic / combined-ext4.img.gz
on EEEPC 701SD which has Atheros AR8121/AR8113/AR8114 PCI-E Ethernet Controller
and Realtek RTL8187SE 802.11b/g PCIE.
However after reboot, ifconfig only shown "l0". No eth0 nor wan0 shown.
I think it maybe the driver issue.
I tried to manually install them. It's hard to find those NIC drivers for linux. So I plan to use ndiswrapper to wrap those windows drivers. But there is no "make" command in the system. No chance to compile and install ndiswrapper.
kmod-atl1e, which is available prebuilt in the OpenWrt x86 repository, should drive the Ethernet. You can use Image Builder to install it into a new image, or mount the card on another machine (ext4 format), leave the .ipk file somewhere in the file system, then boot up Openwrt and opkg install from the file.
Replace that Realtek wifi rather than try to use it. It will never operate in AP mode, which is what you would want when building a router. If the BIOS isn't locked to certain cards, try to find an ath9k model. Or use a USB adapter.
kmod packages will not install or run unless they exactly match the version of OpenWrt. In this case it would be http://downloads.openwrt.org/releases/18.06.1/targets/x86/generic/packages/kmod-atl1e_4.14.63-1_i386_pentium4.ipk
I'm assuming that without Ethernet or wifi drivers, the OpenWrt Eeepc is not yet able to connect to the Internet, so you couldn't do an online install. You will have to download the file using another machine then transfer it.