WPS Office

WPS Office is a Chinese office suite with broad compatibility for Microsoft formats, available across Windows, macOS, Linux, Android and iOS.

Its cross-platform coverage is more complete than Microsoft's own in some respects — a full-featured Linux version in particular — and its mobile apps are more capable than most office apps on a phone.

Compatibility with .docx and .xlsx is good but not perfect for complex documents, so files that must render identically elsewhere are worth verifying before sending.