What setup would you (or other people) recommend for a local model, and which model, if I want something like Claude Sonnet 4.5 (or actually, earlier versions, which seemed to be better)?

Anyone could chime in! I just want to have working local model that is at least as good as Sonnet 4.5, or 3.x.

Nothing open is quite as good as Sonnet 4.5 and Codex 5. GLM 4.6, MiniMax M2, Deepseek v3.2, Kimi K2 and Qwen Coder 3 are close. But those are hundreds of billions of parameters, so running locally is very very expensive.

That is unfortunate. I will never be able to afford such hardware that could run them. :(