The 58xxq has an interesting BIOS. When you get into it the top line of the screen identified it as InsydeH20 Setup Utility Rev. 5.0. In the Linux dmesg text I find the line:
DMI: 10ZiG Technology. 58xxq/Type2 - Board Product Name, BIOS 58xxq V:3.6.21B-1209201 12/09/2014
A later V1.1 example was fitted with:
DMI: 10ZIG Technology. 58xxq/Type2 - Board Product Name, BIOS 58xxq V:3.D.2-01242018 01/24/2018
Hit the ESC key on power-up to get to the startup screen. This is shown below.
There are four icons shown on the screen with the currently selected one being highlighted.
The Boot Manager screen lets you pick the boot device for this particular boot. At the moment
the internal SATA drive is highlighted. (At this time PXE booting was disabled in the BIOS so didn't
appear as an option here).
I was prompted for a password before I could enter this screen. 10ZIG worked.
I find that in the Device Management screen there is nothing to show or do.
The SCU option gets you the conventional BIOS setup. To get into it I was first prompted
for a password and found that 10ZIG worked. (Note upper case).
An example from the Boot setup in the BIOS screen. Note the option there to enable/disable
the ability to boot from a USB device.
Setting the boot order sits under the >Legacy menu item.
My 5817q came with WES7 installed.
I'm so used to manufacturers like HP or Wyse who have extensive support pages from which you can download the original firmware, find updates to the firmware and the latest BIOS that the 10ZiG site comes as a bit of a shock....
The 10Zig website has no obvious download section or support contact - the only immediately obvious thing being a support FAQ that appears under the Resources tab. I note that when you mouse over the 'Contact' tab you get two drop down options: 'Become a Reseller' and 'Career Opportunities'. However, if you actually click on the tab, a new page does appear and down the page there are a couple of email addresses for support.
I spotted one entry in the FAQ:
24 I am trying to get dual HDMI monitors to work on the 58XX (L800) model, each will work but not both at the same time.
Please contact tech support for a BIOS update that will support dual HDMI monitors.
I haven't tried contacting support to see how easy it is for an individual to get hold of original firmware or a BIOS update for a one-off eBay purchase.