“I use LibreOffice Writer and other Linux apps”. There, simple as that.

If they ask why and show a more actual concerned interest, I usually mention Microslop history of privacy invasions and history of deliberate incompatibilities in Office, and recommend a few links documenting that stuff as well as some legal hot waters Microslop has gotten into.

I didn’t use Linux in college, but I did use many FOSS tools. LibreOffice is easily my favorite office suite and there’s no contest. So long as you export your documents as .PDF or submit them as .DOCX, nobody is likely to know or even care what you used to type them.

This is likely to be similar for other types of software- as long as your finished product is compatible and looks good on the proprietary software, you shouldn’t run into any issues.

BTW, the university had student access for Microsoft Office. I could have chosen to use their tools at any time and I simply chose not to.

Most of the time I use MarkDown and export as PDF, if I need more complex layouts I’ll use Libre Office