I happen to own an OSSC (Open Source Scan Converter) and wanted to use it to connect my ZX Spectrum Next to my flat panel. The ZX Spectrum Next does have an HDMI output, but it produces a rolling, waving, wobbly picture. So I connected up its VGA output to the OSSC and started tweaking ...
Some time ago I purchased a DivIDE 2k14 interface for my ZX Spectrum +2. This particular incarnation of the popular DivIDE and DivMMC interfaces seemed like a good choice with its Kempston compatible interface (for those games that don't work with the Sinclair interface built into the machine), and of course four flashable firmware slots, so I could easily switch between Fatware and ESXDOS.
The interface is actually advertised as being flashable, which I guess most people would assume means they can update the flash from software.
As it turned out, this was not possible.