In addition to the desktop version, the portal is also available as a mobile app. It can be downloaded here:

Google Play - DonorView: https://play.google.com/store/apps/details?id=com.donorview.portalapp

Apple iTunes - iOS DonorView: https://apps.apple.com/us/app/donorview-portal/id6758018036

Your constituents will need your portal URL or QR code to activate the portal.