jiapei100

Mainline Linux kernel is from six months ago and one year behind Armbian kernel, also stable version v4.19.y where most of the stuff is regularly back ported. Compiling mainline kernel and expecting (better) functionality is overoptimistic/pointless, especially in case of Banana M3.

You can try new Armbian kernel, but I have no idea if it boots at all on your board, by using armbian-config tools -> system -> alternative kernels.

@Igor
 
Several months passed. I totally forgot... Sorry... Problem solved !!!
Thank you so much... Have a nice day...

Manual for start perhaps?
 
https://docs.armbian.com/User-Guide_Getting-Started/#how-to-connect-to-wireless

before reboot /etc/network/interfaces will be active.
Configure via nmtui and set it active at boot, then save and reboot  - this wil activate the connection

Switching to the supposably better kernel opens a pandora box of problems. If you don't know that, you are probably not capable of fixing them. You can force variables in userspace/lib.config, by adding KERNELBRANCH="branch:v4.15.y". But it is pointless for this particular board family. There are 100+ patches which secures specifics board H3&H5 functions not found in 4.15.y or 4.16.y ... in between and a lot of them will stop working. This means you will certainly fail to build and boot the board. This is how it looks like:
 
 

It is enough. 

This job is not exactly trivial and it is hard to standardize it. However, users usually add cloned boards with minor adjustments directly to the script - We accept their contributions if done correctly and if they don't break anything.
 

You are trying to solve a problem that doesn't exist in a first place - OPi Plus2 works with existing OPi Plus configuration - DRAM size is autodetected by the u-boot/SPL and eMMC size is not hardcoded anywhere too.
 
I case you still want to go your way you need to add the missing DT file to the kernel too, if you provided a text boot log instead of pictures I'd copy the relevant part from it.

There is no such configuration in the Armbian build script. If you added a configuration or made any other modifications to the build script or its configuration you have to fix issues by yourself - add missing device tree files, fix u-boot configuration, etc.

Renaming/disabling the xradio patch file is a better option IMO.

This is caused by 4.14.17 kernel update - at least the xradio compilation is broken.

I believe that the various PI boards do choose a random MAC address most / all of the time.
If it helps you can specify a MAC address in the /etc/interfaces file 
 
Something like this should do it:
 
# Network interfaces allow-hotplug eth0 iface eth0 inet dhcp hwaddress ether 08:00:00:00:00:01