The LLM4Decompile project (https://github.com/albertan017/LLM4Decompile) provides some open models for binary to C decompilation and Ghidra pseudocode refinement, along with some training sets.

RevEng.ai, linked a few times already, discusses their approach here: https://blog.reveng.ai/training-an-llm-to-decompile-assembly...