Massive disclaimer: I am still learning how to touch type. I still have an abysmal 50–60 WPM performance. What I am sharing is my personal experience and the techniques I find valuable. Your mileage will vary.
Touch typing is a technique that involves typing without looking at the keyboard, using the same fingers on predefined parts of the keyboard and resting your fingers on the home row as a starting point. This isn’t a textbook definition, but rather a description you’re likely familiar with if you frequent online forums.
It is especially hard to master for those with preexisting typing habits. It’s very different from so-called pecking.
Added difficulty comes from the effort touch typing demands on standard 60%+ row-staggered keyboards. While your most dextrous finger—the thumb—is expected to press just one huge space bar, your tiny and likely neglected pinky has to do the heavy lifting for special characters and modifiers on both sides of the keyboard.

That’s why I personally believe learning touch typing makes the most sense on ortholinear keyboards with a thumb cluster.
I can support the above statement with two arguments.
First, in this style of keyboard, much of the heavy lifting is shifted to the thumbs. On my keyboard, the thumbs operate SPACE, BACKSPACE, CTRL, ALT/META, COMMAND, and SUPER. The pinky still sees some action—hitting TAB, ESC, 0, and a few common punctuation symbols—but significantly less than on a normal keyboard. This is a fairly common opinion in the split and ortholinear keyboard world.
Now, the second argument is where it all clicked for me. The ortholinear layout means that, for the most part, your fingers only move up and down. Only after realizing this simple fact did I start making progress with touch typing. On traditional row-staggered keyboards, even if we disregard the thumb/pinky issue, your fingers still do quite a bit of dancing—bending and moving along diagonal lines. In an ortho layout, it’s only up and down.

Today, when I type C, the only thing I have to do is move my middle finger one row down from D. When I make mistakes, it is when I catch myself moving my fingers across columns instead of along them.
This up-and-down flow from the home row is, in my experience, the most powerful trick to getting better at touch typing.
An additional trick: Make sure the homing keys are well marked so you can easily return to the correct starting position. Without that, all bets are off.
There are people you’ll see on YouTube reaching 200 WPM on MonkeyType using a traditional keyboard layout. Also, a lot of the ergo scene is just productivity porn or art for art’s sake. Pick what works for you.
Forcing myself to think in terms of vertical finger movement and using an ortholinear keyboard is my trick to finally seeing progressive improvement in typing quality and comfort.