I see lots of links here but no reasons why each is underused or anything.

Look, I’m a simple person, what I ask of a font is:

• differentiate your symbols — I’m talking 1, l, I, and i with more than a single pixel difference at 11pt 90DPI, and the 0 should be clearly less round than O
• be readable. No extra thinness, fancy swirls… look at any default font as an example (Arial or whatever), or most people’s custom web font as a counter-example
• proportionally spaced. I like \thinspace as thousand separator and I cannot lie
• indefinitely usable (for example as part of a game) after a single purchase that I can do as a consumer. Or free/donationware of course

A very tall order I know. So far I’ve reviewed a bunch of fonts (I wasn’t procrastinating why do you ask) and found PT Sans is the best option I’ve seen, so I’m using it, but I hate its Q. It’s basically an O with a tilde below it. Any better options if all you want is clarity and normalcy?

Edit: near the bottom of the replies there’s Hyperlegible. Somehow I had read over that. Seems to check the boxes! I’ll be looking at this closer on my computer later.

Merriweather is great for longer texts. I use it in all book reader apps.

Anonymous Pro is my coding font of choice.

Shout out to 0xProto! Texture healing in a monospaced font is super cool!

There are too many to mention since there’s so much out there.

You can go to a font website like dafont and perform a search for a font or browse different themes/styles and specify in the results that you want Public domain / GPL / OFL fonts.

Almost all of my fonts are released under an attribution license, so they’re free for commercial use and remixing.

https://michaelwmoss.com/typefaces

I love this hyperlegible one from the Braille Institute: https://www.brailleinstitute.org/freefont/