It's very useful to use ShellCheck to check any shell code you write.
The proper she-bang for Bash is
Bash Infinity - Modern boilerplate / framework / standard library for Bash.
Funky - Takes shell functions to the next level by making them easier to define, more flexible, and more interactive.
create-bash-script - Bash script designed to create other bash scripts with argument parsing.
Bash Language Server - Bash language server implementation based on Tree Sitter and its grammar for Bash with explainshell integration.
critic.sh - Dead simple testing framework for Bash with coverage.
Bats - Bash Automated Testing System.
Oh My Bash - Open source, community-driven framework for managing your bash configuration.
Variant - Turn your bash scripts into a modern, single-executable CLI app.
Bash Snippets - Collection of small bash scripts for heavy terminal users with no dependencies.
Parallel bash - Parallel processing of commands in pure bash along with the support of functions.
bashful - Use a yaml file to stitch together commands and bash snippets and run them with a bit of style.
bash_unit - Bash unit testing.