Sdk toolchains libraries
https://marketplace.visualstudio.com/items?itemName=grumpycoders.psx-dev - A Visual Studio Code extension to help with the installation of PlayStation 1 toolchains, and some project templates.
https://ps1.consoledev.net/nugget/ - 'Nugget' is the nickname for the method of compiling PSX executables using a modern GCC.
https://github.com/Lameguy64/PSn00bSDK - The most powerful open source SDK for the PS1 (as far as open source PS1 SDKs go). Not recommended for beginner use.
https://github.com/ChenThread/candyk-psx - CandyK-PSX: A candy shop of tools and libraries for PlayStation development.
https://github.com/ChrisRx/psxsdk - psxsdk is a collection of tools and libraries for Playstation 1 development
https://github.com/pcsx-redux/nugget/tree/main/psyqo - PSYQo is a modern C++ library to develop on the PlayStation 1.