コード解説の代替についてPerplexityで訊くと以下が挙げられた
Codeium, Tabnine
https://swimm.io/learn/ai-tools-for-developers/6-github-copilot-alternatives-you-should-know
Bito
https://bito.ai/blog/free-github-copilot-alternatives-for-vs-code/