Apache OpenOffice is an open-source and free office software suite, and can be used on Windows, MacOS, and Linux. It’s easy to use, has equivalent programs for all of the members of the Microsoft Office Suite, and can be used for personal, business, or other purposes.
OpenOffice Writer is the suite’s word processing software and it is able to open .docx files, generally without encountering formatting issues. Thanks to having been under constant development for over 20 years, it’s a great alternative to Microsoft Word.
Kingsoft’s WPS Office is another free office suite that includes very competent and highly compatible word processing software. It is available for Windows, MacOS, iOS, Android, and Linux, and as an online platform. The downloads are small, the software works well, and it can easily handle .docx files.