No. You do not need to be signed in to any VT login services in order to search in Discovery Search, but signing in will give you the chance to view your library account or save items for later. To access the full text of an article or ebook, click on the link, and if you need to be authenticated as a member of the VT community, you'll be prompted to sign in using 2-factor authentication after you try to access the full text.
When you're looking at the page of results, you may notice a link at the top right corner of the page that says "Sign in":
You can choose to sign in using your VT 2-factor authentication or borrower's credentials (for those not affiliated with the university):
When you sign in with a VT account, you'll be asked which information you'd like to share; select Accept.
For more information, visit the Discovery Search: Accessing Discovery Search Research Guide.