You are able to log into the ChatGPT Android App by using your Microsoft account. You can check out the proper procedure on how to do so with this tutorial from Seeking Tech.
1. To start off, you need to open the ChatGPT Android App if you don’t have it opened already.
2. If you aren’t signed into your ChatGPT account, then you should be in the Log In screen.
If you are signed into the mobile application with a different account, then you need to log out first. In order to do so, tap the hamburger icon on the top left side of the screen. Afterwards, select Settings, scroll down and then select the Sign Out option.
3. From the Log In screen, select the Log In option.
4. On the next screen, you need to select the Continue with Microsoft Account option.
5. You should then be taken to the Log In page of Live.com. From there, you need to enter the email and password you used for your Microsoft Account.
6. When asked if you want to let OpenAI.com have access to your Microsoft Account login information, select the Accept option.
You should now be signed into the ChatGPT Android App via your Microsoft Account.