Due to its proprietary nature, finding software that can properly read those files can be tricky.
LibreOffice is the usual go-to for folks wanting an office suite, that respects privacy, and FOSS. It can read docx files, but it can mess up formatting. Still, for many it’s the preferred choice. It’s got the best reputation.
Now if formatting REALLY matters, take a look at OnlyOffice. It handles those MS formats so much better. It’s not a bad suite, but it’s hard to beat the good reputation Libreoffice has gained.