> It turns out, for years, popular terminals have supported 24-bit color. And yet they’re rarely used.

Hard to say how rarely. I've been using 24-bit color in bash prompts and neovim scheme for a while. Can't go back to 16 or 256 color ones, they are just too limited.

I wish tty terminal also supported 24-bit color.

For setting the color in bash I use something like:

    printf "\x1b[38;2;${r};${g};${b}m"

or

    printf "\x1b[${f};38;2;${r};${g};${b}m"

If I need to set extra bits like bold.