Seems like it could be avoided by phrasing it as "What is your contact information on your preferred platform (discord/bluesky/email, etc.) so that I can get in touch with you?" or somesuch.
Something as simple as adding "username + platform" would give guidance on how to answer it, right now it looks like you're asking for just the platform to contact them on
Comments
Maybe split it into two questions? One for platform and one for username?
I had a friend who worked in tech support have someone writing the word Click on their mouse.
PRICELESS xD