Just a list of Awesome Alt Langs to check out:

• Alpaca - a statically typed, strict/eagerly evaluated, functional programming language for the Erlang virtual machine, inspired by ML
• Arend - a theorem prover based on Homotopy Type Theory. IntelliJ Arend is a plugin for IntelliJ IDEA that turns it into a full-fledged IDE for the Arend language.
• Arturo - Arturo is a modern, dynamic programming language for fast and portable standalone scripts, based on syntactic flexibility
• ATS - a statically typed programming language that unifies implementation with formal specification. It is equipped with a highly expressive type system rooted in the framework Applied Type System, which gives the language its name. In particular, both dependent types and linear types are available in ATS.
• Beef - an open source performance-oriented compiled programming language which has been built hand-in-hand with its IDE environment.
• Ć - a programming language which can be translated automatically to C, C++, C#, Java, JavaScript, Python, Swift, TypeScript and OpenCL C.
• caramel - a functional language for building type-safe, scalable, and maintainable applications.
• carp - A statically typed lisp, without a GC, for real-time applications.
• Clean - a general purpose, state-of-the-art, pure and lazy functional programming language designed for making real-world applications.
• Clio - a functional, parallel, distributed programming language.
• Coconut - Simple, elegant, Pythonic functional programming.
• CoffeeScript - an attempt to expose the good parts of JavaScript in a simple way.
• crystal - a language for humans and computers.
• Efene - Efene is an alternative syntax for the Erlang Programming Language focusing on simplicity, consistency, ease of use and programmer UX.
• F* - a general-purpose functional programming language with dependent types, monadic effects, refinement types, and a weakest precondition calculus.
• Felix - an advanced, statically typed, high performance scripting language with native C++ embedding.
• Fennel - Fennel is a programming language that brings together the speed, simplicity, and reach of Lua with the flexibility of a lisp syntax and macro system.
• flix - a statically typed functional, imperative, and logic programming language with advanced features that compiles to JVM bytecode.
• Futhark - high-performance purely functional data-parallel array programming.
• Gerbil Scheme - Gerbil is a meta-dialect of Scheme with post-modern features
• gleam - a fast, friendly, and functional language for building type-safe, scalable systems!
• Golo — a lightweight dynamic language for the JVM.
• Go+ - The Go+ programming language is designed for engineering, STEM education, and data science.
• GOO - type-based prefix syntaxed language that is simple, powerful and extensible.
• grain - a new language that puts academic language features to work.
• Hy - Hy is a Lisp dialect that’s embedded in Python
• idris - A Language for Type-Driven Development.
• inko - Safe and concurrent object-oriented programming, without the headaches.
• io - a programming language focused on expressiveness through simplicity.
• J - a high-level, general-purpose programming language that is particularly suited to the mathematical, statistical, and logical analysis of data.
• Janet - a functional and imperative programming language.
• koka - A Functional Language with Effect Types and Handlers.
• Lumen - An alternative BEAM implementation, designed for WebAssembly.
• MoonScript - A programmer friendly language that compiles to Lua.
• mun - a programming language empowering creation through iteration.
• nim - a statically typed compiled systems programming language.
• Odin - The Odin programming language is designed with the intent of creating an alternative to C with the following goals: simplicity, high performance, built for modern systems and joy of programming.
• Passerine - A small extensible programming language designed for concise expression with little code.
• Pharo - a pure object-oriented programming language and a powerful environment, focused on simplicity and immediate feedback.
• picolisp - a programming language, or really a programming system, including a built-in database engine and a GUI system! It's simple and lightweight and encourages clean, concise code.
• pony - an open-source, object-oriented, actor-model, capabilities-secure, high-performance programming language.
• pyret - a programming language designed to serve as an outstanding choice for programming education while exploring the confluence of scripting and functional programming.
• red - a next-gen programming language, strongly inspired by REBOL.
• ReScript - The JavaScript-like language you have been waiting for. Previously known as BuckleScript and Reason.
• Shen - a hypermodern functional language that offers many features not currently available under other functional platforms.
• unison - an open source functional programming language based on a simple idea with big implications: code is content-addressed and immutable.
• Unseemly - the first language able to safely typecheck all macros before expansion.
• v - Simple, fast, safe, compiled. For developing maintainable software.
• wren - a small, fast, class-based concurrent scripting language.
• zig - a general-purpose programming language and toolchain for maintaining robust, optimal, and reusable software.
• zz - zymbolic verifier and tranzpiler to bare metal C.