Microsoft has published the following notification for their planned end of support for Teams on Android 4.4:

Microsoft will be retiring the Teams support on Android 4.4. It is recommended that users upgrade to newer Android builds, which is where Microsoft will continue to invest.
Key Points:
  • Major Retirement
  • Timeline: August 1, 2020
  • Action: Review and assess impact
How this will affect your organization:
If you have devices running Android version 4.4: the exiting Teams build 1.0.0.2020050801 will continue to work on Android 4.4 for the next 2 months but there won’t be any app updates going forward.
What you need to do to prepare:
Instead of using Android 4.4, Microsoft recommends updating the Android OS version to 5 and above.