Apple’s own Terminal.app supports 24 bit color in Tahoe. Not sure if you were already aware, which sparked the question, or not.

When you say Terminal app, do you really mean shell commands? i.e. do you want to run something in Terminal.app that will demonstrate the expanded colour range?

Try btop, a resource monitor with true colour support and 37 builtin themes.

iterm, it's the best

If I am not mistaken, Alacritty does [1]. I believe iTerm2 and Kitty support 24 bit color too.

[1] https://github.com/alacritty/alacritty