To use Termux:GUI in fullscreen mode, you have a few options depending on your setup:

1. For Termux:X11 (if you're using X11 apps):

   • Open Termux:X11 settings and look for the "Fullscreen" option. Enable it there. This is the most straightforward method for X11-based GUI apps running through Termux:X11. Some users report that this works best when not using Samsung DeX mode, as DeX may interfere with fullscreen behaviorreddit.com.

2. For Termux:GUI (native Android GUI plugin):

   • The Termux:GUI plugin itself supports setting an Activity to fullscreen via its API. If you are developing or running a custom GUI app using Termux:GUI, you can use the plugin's features to set your app to fullscreen programmatically. This is documented in the plugin's README and requires some knowledge of how the Android GUI worksf-droid.org.

3. For the Termux terminal (not GUI):

   • You can enable fullscreen mode by editing the Termux properties file. Create or edit ~/.termux/termux.properties and add the following lines:

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     fullscreen=true
     use-fullscreen-workaround=true

   • After saving, either restart Termux or run termux-reload-settings for the changes to take effect. Note that on some Android versions (like Android 13), you may still see the gesture pill or navigation bar, as fullscreen support can be inconsistentandroid.stackexchange.com+1.

4. Using Tasker or ADB (advanced):

   • Some users automate fullscreen mode using Tasker to enable immersive mode when Termux launches. Alternatively, you can use ADB commands to force immersive mode, but this requires USB debugging and is more technicalreddit.com.

If you are specifically using Termux:X11, the built-in fullscreen toggle in its settings is your best bet. For native Termux:GUI apps, you'll need to implement fullscreen in your app code using the plugin's API.

Would you like more details on any of these methods, or are you using a specific setup (e.g., Termux:X11, native Termux:GUI, or the terminal)?