My favourite library from these folks is gum (https://github.com/charmbracelet/gum). The basic premise is simple - instead of using hardcoded variables or in addition/instead of using CLI flags, call gum and capture the STDOUT to get the selected input value(s). Great for turning a bash script into a TUI, uses these libraries under the hood.

I find the pattern of showing interactive TUI if required options/flags are omitted much nicer than showing an error/help output.