Libadalang - Library for parsing and semantic analysis of Ada code.
Ada Language Server
GNAT LLVM - Experimental Ada compiler based on LLVM, connecting the GNAT front-end to the LLVM code generator.
Introduction to Ada Programming (HN)
HN: Airbus Chooses GNAT Pro Ada for Development of Unmanned Aerial System (2020)
Alire - Catalog of ready-to-use Ada libraries plus a command-line tool. (Code) (Article) (HN)
Cowgol - Self-hosted Ada-inspired programming language for very small systems.
Ada Improvements Ideas
HAC - Experimental Ada compiler, fully in Ada. (Web)
Giving Ada a chance (2021) (Lobsters) (HN)