Microsoft is introducing ads into a free version of Office, which seemingly only lets users save to OneDrive.

In other news, LibreOffice is also free, doesn't have ads, and lets you save your documents wherever you want. I use it every day for my work. It is available here:

https://www.libreoffice.org/

Home | LibreOffice - Free and private office suite - Based on OpenOffice - Compatible with Microsoft

Free office suite – the evolution of OpenOffice. Compatible with Microsoft .doc, .docx, .xls, .xlsx, .ppt, .pptx. Updated regularly, community powered.

@neil
I use Open Office, and I have been relatively happy with it, over the last 15 years. It can save as and open Office files (including Excel).
@Darkphoenix You might want to read this, as OpenOffice has multiple unfixed security issues over a year old, so it's risky to stay with it: https://en.wikipedia.org/wiki/Apache_OpenOffice#Security
Apache OpenOffice - Wikipedia