Heya,
In the past three years, I have worked extensively with the vga test suite that xjas did an amazing job to collect together in the thread you linked to. By extensive, I mean analysing signal dumps and developing FPGA boards to capture, synchronize and display most of the video modes presented in that suite.
These are really nice demos, and that assembled vgasuite paints a picture that maybe there would somewhere exist that "ultimate" most compatible setup that would support all the different possible modes.
However, I would like to shatter that idea a little bit. Let me summarize my thoughts on some of the different demos:
Ambience + Luminati: These demos share the same effect, namely running at a high refresh rate, and then outputting two different video streams on alternate frames, depending on CRT phosphor persistence to blur them together. These would require > 120 Hz LCD displays to work, but unfortunately on such displays, these demos are expected to still look poor, since the original demo effect required phosphor persistence on the CRT to blur the video frames together. Modern LCD display pixel switching speed is too high quality to reproduce this effect like it used to be.
Timeless (56Hz): this demo increases the number of vertical scanlines per frame in Mode 13h from default 449 lines to 561 lines, spending that time in video blank. The net effect is to reduce the video refresh rate from 70Hz down to 56Hz. Good scalers and LCD monitors should have no problems with this mode.
Dowhackado: A custom 320x256 pixels @ 55 Hz video mode. Should pose no problems to any good scaler.
Kukoo 2: This demo uses a custom 397x557 @ 55Hz px video mode. Beyond this custom mode, which should be easy to support, the main color "magic" of this demo is done on the VGA adapter end, so all scalers and CRTs/LCDs will be compatible with the palette stuff that happens there. (they don't "see" that part at all, as it happens earlier in the VGA card)
Copper wobble: This demo radically abuses the VGA adapter by reprogramming the video geometry on the fly on every scanline. This behavior is not just problematic on many CRTs of the time, or video converters, but absolutely problematic already on different VGA adapters. There is no standard on what should happen with the different operations they do, and the demo probably worked on only a very specific adapter + CRT combo that was compatible with their very specific timings. It could even be harmful and damage other CRTs. There is no other piece of software or even demoscene demo out there that would use this same functionality, so it is not like this demo would represent a sensible "class" of functionality or some kind of feature compatibility that a good CRT/scaler/LCD should have. As result, it would be a stretch to call what Copper does even a "video mode" - it was just a radical abuse of VGA adapter parameters that worked on a particular VGA adapter + CRT combo timings at the time. Overall, it is best to ignore that this piece of software ever existed. (this may be a bit harsh to write, though it of course was a fantastic hack, but what they do is at odds with other more interesting goals of stable video signal synchronization in a scaler device, and nothing else needs this functionality beyond this one demo.. placing it on a pedestal would be counterproductive)
Sunflower: This demo is just standard video modes: 640x480 and 320x200.
Yo and Impulse Tracker: Both are 640x400 @ 70 Hz. This is a tiny tweak on standard 320x200, should be a very compatible video mode.
Cubic Player: standard 720x400 text mode.
Tweak, PAL-on-VGA and NTSC-on-VGA: Very compatible video modes as well with many LCDs. If e.g. Mode-X is supported, I'd expect these to be quite well supported as well.
CRT Terminator Digital VGA Feature Card ISA DV1000 supports all these video modes, with the exception of capping Ambience + Luminati video output to 75 Hz max (the reason for this is artificial, since I haven't found a LCD display that would support >75Hz refresh rate on DVI-D compatible signal), and not synchronizing to the Copper wobble: instead, it regards it more important to assume stable video geometry to help fast video syncing and signal stability.