Probably the two most popular free implementations of Common Lisp are Clozure Common Lisp (CCL) and Steel Bank Common Lisp (SBCL). They are both available for a variety of platforms including Linux on x86-64 and Linux on ARM.
Besides the compiler and basic Read-Eval-Print Loop (REPL), you may want some sort of development environment. One popular setup is to use Emacs to edit text interactively. The Superior Lisp Interaction Mode for Emacs (SLIME) allows Emacs to connect to a Lisp implementation and evaluate code interactively, from the editable text file and from a REPL within the Emacs editor: