Given the direction they're going with the web versions of Office 365, it's entirely possible that the future involves them deciding porting stuff to the Windows version is not economically viable and relegate the native apps to legacy support like IE.

I've been 100% Office 365 web apps on Linux Chromium since around February. So far, I haven't hit a situation that has required spinning up my Windows 10 VM.

What do you do when you want to edit a document or compose an email offline?

I don't know. I'm in a US coastal megalopolis covered in cell data towers, so I haven't encountered that issue yet. I'm sure it will happen at some point, but I think the web apps have offline capability.

I am guessing Office 365 has some sort of offline capabilities. Maybe not?

For the email, can’t you write it anywhere? Difference is it’s not officially a draft in an email client.

Office 365 allows you to install the latest version of word excel ... too in addition to their web versions. It’s actually the superior part of the offering, even though Hm tends to focus on the web part (why superior ? Automatic upgrade to latest so no mismatch of versions inside your company, no expensive acquisition cost merely add less than ten euro a month to add a new user, disable the next month if it didn't work out).

The installer fails on wine last time I checked, but porting an installation from windows works fine, and the account and license connection is fine too.

Office 365 is 700 things all with the same name.

Office 365 web apps (free), Office 365 the monthly updating desktop Windows version of MSOffice (not free)

Outlook webmail works fine offline. You need to enable some setting though.

That's actually kind of happened. One note program is no longer part of Microsoft office anymore. Instead you are suppose to use the onenote app. It's a hassle but you can install the old program and it's still much better than the app