Your best option would be to use onlyoffice. Not sure what you mean by copilot. Copilot is available in vscode, vim, jetbrains, all of which are cross platform. You can also try using bavarder if you want something like chatgpt.
I personally use a small tool called mods to access gpt 4 using an openai API key in my terminal, but this option is only great if you have a terminal heavy workflow.