Office 2021 and Office LTSC 2021 reach end of support on October 13, 2026, with no paid extension, according to Microsoft's lifecycle page.
Over five years, Office Home 2024 at $149.99 costs about a third of Microsoft 365 Personal at $99.99 a year.
Office 2021 also loses Microsoft's support for connecting to Exchange Online, SharePoint Online and OneDrive on that date.