You can use a mobile device as a digital writing surface in Google Jamboard or during a Zoom meeting. Using this method, an inexpensive stylus will vastly improve the writing experience. Styli are widely available on Amazon at a variety of price-points.
If using Google Jamboard, simply open up the Jamboard app on your mobile device. You will remain on the Zoom meeting on your computer for video and audio communication. (See the above section on Google Jamboard.)
If using the Zoom whiteboard, there are several ways to connect your mobile device:
Join the Zoom session from both your computer and your iOS or Android device. Use the computer for video and audio communication, and the mobile device for accessing the whiteboard. (Make sure you mute the audio on your mobile device.)
If you have an iOS device (iPhone or iPad), you can connect it to your computer and share your device’s screen as a secondary source.
If you have a newer Mac and iOS device, you can use Apple’s Sidecar feature to connect your iPhone or iPad as a second touchscreen display.