Telegram does not support accounts protected with two-factor authentication.

[Gregory Opera]

Telegram version 2.0.4.0

bq Aquaris E5 HD Ubuntu Edition:
* OS build number: OTA-9
* Ubuntu Image part: 20160123.1
* Ubuntu build description: Ubuntu 15.04 - armhf (20160123-115651)
* Device Image part: 20160108-efc96d8
* Device build description: VEGETA01A-S23A_BQ_L100EN_2009_160123
* Customization Image part: 20160111-926-36--vivid

Reproduce:
- Login to Telegram on a computer with a telephone number and enable two-factor authentication.
- Open Telegram on Ubuntu mobile device.
- Attempt to login with existing telephone number.
- Close Telegram ("swipe away").
- Open Telegram on Ubuntu mobile device and attempt to login with existing telephone number a second time.

Result:
Initial attempt to login to Telegram with telephone number results in an error message saying that two-factor and/or password protected accounts are not supported, subsequent attempts to use Telegram load a white screen and cause a text message to be received stating:
You are using an outdated app that doesn't support 2-step verification. Please update your app to log in to Telegram.

Expectation:
To be able to login to and use Telegram using an existing account, with two-factor authentication enabled.