SoftMaker published the latest stable version of its free (but not open-source) office suite FreeOffice 2021. Free Office is one of the best free Microsoft Office alternatives which is available across Windows, Linux, and macOS. SoftMaker’s FreeOffice is totally compatible with Microsoft Office file formats.
FreeOffice 2021 features

The company released the commercial version of their popular office suite SoftMaker Office 2021 last year. The developers announced the new free version is completely revised. You can find the new features of each application of FreeOffice 2021 listed below:
TextMaker 2021
The Microsoft Word alternative now supports the simultaneous use of footnotes and endnotes in the same document.
PlanMaker 2021
The Microsoft Excel alternative now offers extended pivot tables and conditional formatting.
Presentations 2021
The new Presentations version is now more compatible with Microsoft PowerPoint than before. It also offers new animation and slide transitions based on OpenGL.
Download FreeOffice 2021

If you are looking for a free Microsoft Office alternative for your Linux operating system, FreeOffice is one of the best options other than LibreOffice. Despite it being not open-source, FreeOffice is more compatible with the Microsoft Office applications than before.
You can download FreeOffice 2021 for free. On the official website, you can find the installers for Windows, macOS, and Linux.