While Microsoft prefers Click-to-Run, some direct image links (IMG files, which work like ISOs) have been verified by Microsoft Support contributors as safe, official mirrors: Office 2021 Professional Plus download link - Microsoft Q&A
<Configuration> <Add OfficeClientEdition="64" Channel="PerpetualVL2021"> <Product ID="ProPlus2021Volume" PIDKEY="YOUR-VL-KEY-HERE"> <Language ID="en-us" /> </Product> </Add> </Configuration> While Microsoft prefers Click-to-Run