Linux

Office 365 on the web works well on Linux if that has enough functionality for you. If not, the only way to get a modern version of the real Microsoft Office is in a VM. Older versions will run over Wine.

As far as alternatives go, OnlyOffice has the best reputation for file compatibility. I use LibreOffice and am very happy with it.

Avoid OpenOffice. It is really just an ancient version of LibreOffice.

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.

You don't (sorry)

OnlyOffice has fantastic support for Microsoft originated documents. I typically use the Flatpak version. The look and feel is very similar to the office suite so you should be “right at home”.

If you have to you can, sometimes. But you should use alternatives, if possible.

Web apps

There's Onedriver to connect onedrive on Linux. Though it's been a while since I last used it.

The flowchart is as follows:

LibreOffice or OnlyOffice for desktop apps (no, they are not Microsoft apps, but yes they use Microsoft formats and can edit and save Microsoft documents/spreadsheets/etc). OnlyOffice is the closest of the two to the Windows experience.

If you really aren't open to using alternative software (which is strange given that you're using Linux), then the web apps exist. I've heard they're really close to the actual desktop suite, though I don't have any interest in ever using them as we have very good free and open source alternatives available (see above).

If the web apps don't cut it for you, then you can run the official apps in a VM, or maybe through WINE. Here's the WINE DB page for Microsoft Office, which lists various Office versions and their level of compatibility through WINE.

~~Copilot will likely not be possible to secure on Linux in a standalone desktop app (unless someone somewhere hacked something together through Electron to use a web version)~~. Another user said that Copilot is available inside Microsoft Edge, so I suppose you could install that, though I'd highly discourage that. Reliance on LLMs is quite frankly a plague to society, and often feeds incorrect, biased, or purely fabricated responses, as LLMs merely attempt to predict what word is most likely to occur next based on a set of training data, none of which was vetted for accuracy, racism, zionism, sexism, etc. LLMs like copilot do not have any form of intelligence, and do not understand what they are saying. I highly recommend you just use a search engine in your browser, because it'll feed you the same info all the LLMs were trained on anyway.

OneDrive recently received native support in GNOME, so I think you should be able to access it in your settings under accounts/connected services (whatever GNOME calls it nowadays)? I've never tried to use it, so other people will know better than I will there, but it should be possible to use.

I mean. does o365 not work or you specifically want to run the exe's?

You could use libreoffice apps and then convert it to Microsoft formats to share with your coworkers.

Idk if this has been proven, but I'm certain that the current desktop versions of Office apps are just Electron-style wrappers for the web versions. I switched from Windows to Linux about a year ago and have found the web apps to be perfectly sufficient