https://www.techradar.com/news/the-microsoft-stores-unauthorized-libreoffice-app-requests-cash-and-webcam-access

The enormously popular open source office suite LibreOffice has appeared in the Microsoft Store – with an alarming surprise. LibreOffice is an open source project and has always been free to download, even for commercial use, but the app in the Microsoft Store carries a price tag of $2.99/£2.49.

The app description suggests this is just a way for the software's creators to solicit donations, and selecting 'Free trial' rather than 'Buy' will download the full suite with no strings attached.