I find it much easier to fall asleep when the light is redder. Even for example when reading a book, if there's a lot of bright light in the room I will have a much harder time falling asleep.
I've noticed that if I wake up for some reason at night and turn the lights on, if the light is bluer it will tend to wake me up completely, whereas a red light will allow me to stay "sleepy" and fall back asleep quicker.
You are correct, however, that's a confounding problem. The (relatively) weak effectiveness of software solutions is due to blocking only a small percentage of blue light from a (relatively) strong light source (assumes short distance to screen, low ambient light at night).
Blue light (and even some green light frequencies) is a hardwired stimulus feeding into your circadian rhythm. Blocking all blue and green frequencies, e.g. with simple welding glasses, is effective in supporting the creation of melatonin.
But again, having enough melatonin in your system is a necessary but not sufficient condition to be able to sleep.
I still read a lot on computer in the evening, but I get sleepy much earlier.
The problem is that we keep our brains active late at night and that's the reason why it is hard to get to sleep.
For me alcohol is the one that messes with my sleep. The lack of deep sleep makes me feel tired the next day(s).
Edit: an article about recent studies: https://time.com/5752454/blue-light-sleep/