I found a discarded LG Flatron E2260, not the most recent monitor, but functional enough. Long story short, it turned out to be a classical case of dead capacitors.

However, even if colours are OK relative to one another, compared to the built-in LCD, they're still very blue (test made with calibrated internal LCD and f.lux disabled). Worse, f.lux doesn't appear to have any influence on the colour balance when I do turn it on.

The built-in monitor menu is still very limited: preset temp colour can either be sRGB, 6500K, 7500K, 8500K, 9300K, plus three gamma levels. Of course there's a manual option to adjust all three primary colours relative to one another. I don't know how to do that properly, though.

Any help appreciates