Hi there, welcome to this community.
Lyra framework was designed to showcase all advanced features available in UE5, such as “geometry scripts”, developed to support building the levels with procedural meshes, “common UI”, which improves cross-platform development, navigation with gamepads and also uses a layered approach, and the “game features” plugins that represent a modular design for games, mostly used in Fortnite, in which new content can be added or removed without modifying the main game (project content folder). In Lyra, these main plugins are Shooter Core, Shooter Explorer, Top Down Arena and Shooter Maps.
I agree with Ares9323 that GAS is not a good starting point for absolute beginners. In addition to the sources mentioned, the official documentation for GAS is available at:
GitHub - tranek/GASDocumentation: My understanding of Unreal Engine 5’s GameplayAbilitySystem plugin with a simple multiplayer sample project., where you find two example projects, “GAS Documentation” and “GAS Shooter”.
An overview of Lyra Framework:
A brief explanation of Game Features:
I wish you success.