Now that Chrome OS 75 is slowly rolling out again, Chromebook owners will be able to use the built-in “reader mode” for distraction-free browsing it includes. Unfortunately, the experience of switching a web page from its traditional view to reader mode is a bit esoteric. However, a change is in the works to make it easier with a dedicated icon switch.
Currently, to use reader mode you have to enable this flag: chrome://flags/#enable-reader-mode. Then you click the three-dot Chrome menu and choose the “Distill Page” option.

Here’s a description of the upcoming change:
Display Reader Mode icon in omnibox.
This adds an icon that toggles Reader Mode on and off for the current
web contents. It is only visible when the enable-dom-distiller switch
is set to true, either via command line or via chrome://flags.
Frankly, this is how this feature should have rolled out in the first place from a usability standpoint. However, as is often the case with Chrome OS, functionality – often hidden and not explained well – comes first and refinement then follows. The new icon may also have an explainer for users upon first appearing:

As for when this icon switch will follow, I can’t say yet.
There’s no release date tagged to the bug for this functionality, which is still listed as a “work in progress”. Additionally, this new reader mode icon won’t be just for Chromebooks; it will arrive on the Chrome browser for all supported platforms.