It's UNIX, just open Terminal.app

Sometimes that covers the need.

Most will at least want something like https://brew.sh/ to get you current versions of standard Linux utilities rather than the bundled ones and then maybe even set up a separate profile in your terminal of choice (iTerm2 is a great option as well) which defaults to using them so you don't break normal system usage which assumes the built in utilities.

Even then, if your use case requires using standard Docker images, assumes certain features of the kernel, or assumes common distro environments rather than just you wanting a posixy feeling terminal you'll still need to run a Linux VM in the background.