Hi KZC,
Thank you for reaching out to the Microsoft Q&A platform.
Based on your question description we understand that you want to Install Office 2021 in windows docker container.
Unfortunately, Microsoft Office currently does not support containers.
This is because Office applications are designed to run on full Windows operating systems, which have a graphical user interface and other dependencies that are not typically available in container environments.
Please refer the similar issue:
https://zcusa.951200.xyz/en-us/answers/questions/619983/install-ms-excel-on-windows-container-image
Thank you.