Quick answer: A microphone is not required. Official text chat supports the whole game and intentionally becomes unreadable across distance or soundproof barriers, just as voice becomes inaudible.
Communication tools still matter
Text chat interacts with in-game tools such as walkie-talkies. External chat can bypass intended communication situations, so the developer strongly recommends staying in-game.
Keep walking
Big Walk Walkie-Talkie: Verified Basics
Learn the officially described role of Big Walk walkie-talkies in proximity communication without relying on guessed spawn locations or puzzle routes.
Big Walk Accessibility and Motion Sickness SettingsFind official Big Walk options for challenge skipping, rebinding, crosshairs, hold or toggle controls, FOV, and motion-reduction overlays.