Execute function in bash on every keystroke in interactive shell

I would like to run a function every time a user presses a key in an interactive bash shell. I am wondering if bash has anything built in like the self-insert function in zsh? Alternatively, I am wondering if there is some file descriptor I could read from that contains the buffer, similar to the $BUFFER variable in zsh? Note: I am aware of this question: https://superuser.com/questions/604812/how-to-execute-a-function-in-bash-or-zsh-on-every-letter-being-typed-into-prompt . I am looking to build something similar to the script command but without using pseudo-terminals