I've managed to start up the desktop now though the resolution is still very low only at 1024x768 at the moment.
The error message regarding the bus stuff is irrelevant. So forget about it.
The only issue matters here is regarding the video driver. Not sure if it is a Ubuntu bug or Oracle VB's issue. Nevertheless, in RedHats they have similar issues before and they kindly got it fixed years ago. See here "https://bugzilla.redhat.com/show_bug.cgi?id=546166" and I'm really surprised that Ubuntu just has ignored this for so long.
So if you are just like me doing some UEFI test and can tolerate the low 1024 * 768 resolution then here is the remedy.
1. Install Ubuntu under UEFI as normal and when it finishes you will find you cannot boot to the desktop but only a console. Note sometimes the focus will not stop at the VT1 and so you need to manually switch by Crl+Alt+F1 to the virtual terminal.
2. Run "Sudo X -configure" and copy the resulting file into your "/etc/X11" folder using the command "sudo cp xorg.conf.new /etc/X11/xorg.conf" and then modify it.
3. Basically you need to add one line into that file but I'm not sure if it really makes sense. I guess it might also be fine without that line. Nevertheless let's just add it. What need to be edited in xorg.conf is to add a line for "Modes" in the Display subsection of the Screen section at the end of config file.
Note: There're many "Screens" in the file and you need to change the one whose Device section is fbdev.
Viewport 0 0
4. Then, start the graphical server with this command:
### Available Driver options are:-
### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
### [arg]: arg optional
#Option "ShadowFB" # [<bool>]
#Option "Rotate" # <str>
#Option "fbdev" # <str>
#Option "debug" # [<bool>]
VendorName "InnoTek Systemberatung GmbH"
BoardName "VirtualBox Graphics Adapter"
and at this stage you should see your desktop is back.
5. The final step is to make VB automatically start the Unbuntu system. Unfortunately, Oracle's UEFI implementation has lots quirks and one of the most annoying one is it has a goldern fish's memory on the NVRAM. Whatever you assigned as a new value to the vars in NVRAM once virtual machine is turned off or just restarted all your values are gone. So I'm really wondering if that is the case, how can it be called NVRAM (non-volatile RAM) then?
This is just the reason why so many people after installing Ubuntu under UEFI in VB only to get a shell when re-start their machines.
Luckily, this issue is quite easy to fix and my approach here is a one-off approach so that next time when you boot your machine you will get your desktop in a straight way.
To do it, simply follow the steps here. Note you need "sudo" to do all of it.
mkdir -p Microsoft/BOOT
echo "1" > Microsoft/BOOT/bootmgfw.efi
5.2 Install Ubuntu's "Boot-repair" tool (I'm sure you know how to get it) and then run it.
5.3 Choose "Advanced Options" -> "Main Options" and make sure "Use the Standard EFI file" and the following "Backup windows EFI file" is enabled.
5.4 If you want quick fix then go to "Other options" and disable all the options there and then apply.
At this moment you should find when restarting your machine the familiar menu will come up and when you choose Ubuntu it will take you all the way through to the desktop.
Hope this can help people still seeking a solution to the issue.