In the 80's the encyclopedia filled the same niche that a smartphone does for me now. Whenever I had a small number of minutes to kill I grabbed a random volume and flipped open to a random page.
Like you, I am remembering the serendipity of the encyclopedia (and libraries for that matter).
Open two tabs with random wikipedia articles. See how many clicks it takes to get from the first article to the second by just clicking links.
It's pretty fun and educational.
Now, SEO spam has convinced me it's actually a bathtub curve, and is rapidly shooting back up.
This makes sense, historically. I'm sure there was a time when literally anything that had been printed on a printing press was worth reading.
I witnessed the time when anything that had been stored on a CD-ROM was worth reading, since generating CD-ROM worth of data, then producing them was ridiculously expensive (that time period lasted about 1-2 years).
Anyway, early internet, it was hard to publish stuff. As of this year, it's less expensive to write and publish stuff than it is to read it, so curated repositories that are hardened against spam are going to be important again.
Perhaps even better would be if, instead is drawn from the entire Wikipedia, the list was generated from a pool of articles that are at most N links separated from your current page.
I took this to mean the niche is "learning something interesting in a short amount of time" not "killing a short amount of time" so to me the OP implied they were using the smartphone to learn and not browse TikTok.
This behaviour is normal today, but 40 years ago people other than me had the ability to wait patiently.
There's something to be said about not having ubiquitous portable distraction devices to encourage more "productive" uses of time.