If a file claims to be "Office 2021 Portable," it is almost certainly one of three things:
Learn to use LibreOffice Portable or OnlyOffice for 95% of tasks. The 5% where you need native MS Office isn’t worth the keylogger risk. microsoft office ltsc pro plus 2021 portable
Not portable (needs browser), but if you have internet, Office.com gives you Word, Excel, and PowerPoint for free with basic features. If a file claims to be "Office 2021
