Last spring Mistral (free tier) was better for my usage (mainly JS programming) than ChatGPT (free tier). No idea which is better now (esp. after openai launched chatgpt 4, but Mistral improved too) but at least Mistral isn't bad at all.

I don't think I have to elaborate on Linux > Windows. If that's really needed ask for it please. Summary: It's simply better, the times where it was only for nerds are long gone.

Search engine doesn't matter too much. I usually use DuckDuckGo and it works fine (does what a search engine should do without displaying ads, unlike Google).

Signal over WhatsApp also is pretty obvious, but it's the hardest one to change because so many people simply don't want to switch once one thing is running and you want to communicate with those people.

LibreWolf basically is Firefox (which is far better than Chrome in terms of privacy, ad blocking, customisability, ...)