docs: add backspace issue to termux.md

Author: jsjoeio

docs/termux.md

@@ -7,6 +7,7 @@
   - [Upgrading](#upgrading)
   - [Known Issues](#known-issues)
     - [Search issue](#search-issue)
+    - [Backspace not working](#backspace-not-working)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
@@ -16,7 +17,7 @@ Termux is an Android terminal application and Linux environment, which can also
 
 ## Installation
 
-1. Install Termux from the [Google Play Store](https://play.google.com/store/apps/details?id=com.termux&hl=en_US&gl=US)
+1. Install Termux from the [Google Play Store](https://play.google.com/store/apps/details?id=com.termux)
 2. Make sure it's up-to-date by running `apt update && apt upgrade`
 3. Install required packages: `apt install build-essential python git nodejs yarn`
 4. Install code-server: `yarn global add code-server`
@@ -44,3 +45,17 @@ ln -s $PREFIX/bin/rg ./lib/vscode/node_modules/vscode-ripgrep/bin/rg
 ```
 
 For more context, see [comment](https://github.com/cdr/code-server/issues/1730#issuecomment-721515979).
+
+### Backspace not working
+
+There is a known issue with the backspace key not working correctly when using the on-screen keyboard on Android. This is due to an upstream issue. Read more:
+
+- [Issues with Backspace in Codespaces on Android (Surface Duo)](https://github.com/microsoft/vscode/issues/107602)
+- [Support mobile platforms](https://github.com/xtermjs/xterm.js/issues/1101)
+
+Workaround: use a Bluetooth keyboard.
+
+For more context, see issues:
+
+- [500 error: 3.9.2 not working on Android + Termux](https://github.com/cdr/code-server/issues/3036)
+- [Document Android backspace issue](https://github.com/cdr/code-server/issues/3079)