I got the same error. I found a version for FireStick that solves the problem for me.Just installed the latest APK on my NVDIA Shield 2019, the app opens up fine but when I go sign in it gives me an error msg "You don't have an app that can do this" any idea what I'm doing wrong...? Don't have any older versions installed and the Shield is up to date.
Installed these two.
Xfinity Stream BETA MODDED 18.104.22.168 - PURE ANDROID MODDED VERSION (UPDATED)
NEW ICON (Shortcut) Xfinity Stream - PURE ANDROID MODDED VERSION
Xfinity Stream (Fire TV / Android TV) 22.214.171.124 (Android 7.0+) APK Download by Comcast - APKMirror Free and safe Android APK downloads