Or, I don't know, install the latest Emacs, open a terminal that supports 24bit xterm, and do: emacs -nw If it looks good when you apply a theme, great.

Or, I don't know, install the latest Emacs, open a terminal that supports 24bit xterm, and do: emacs -nw If it looks good when you apply a theme, great. If not add the following to .bashrc, .zshrc, .fishrc (you know the drill): export COLORTERM=truecolor (reload the shell, or just execute this line and start emacs -nw again, voila.) For some reason, this article makes it look like you need to dig into terminfo, generally you won't need to, maybe 10 years ago, not now. (I quickly retested just now, to be sure, on Macos iTerm & Linux, Alacritty, Kitty, Gnome Terminal. 24Bit xterm is commonly supported these days.)