diff --git a/.github/workflows/ppa-release.yml b/.github/workflows/ppa-release.yml
index e8fa5ac..84805ac 100644
--- a/.github/workflows/ppa-release.yml
+++ b/.github/workflows/ppa-release.yml
@@ -18,7 +18,6 @@ on:
         options:
           - jammy # 22.04 LTS (also Linux Mint 21.x, Pop!_OS 22.04)
           - noble # 24.04 LTS (also Linux Mint 22.x)
-          - questing # 25.10
           - resolute # 26.04 LTS
       tarball_suffix:
         description: 'Tarball suffix (e.g., ds1, ds2) - leave empty for new releases'
@@ -46,8 +45,8 @@ jobs:
             echo 'releases=["${{ inputs.ubuntu_release }}"]' >> $GITHUB_OUTPUT
             echo "Dispatch: building only ${{ inputs.ubuntu_release }}"
           else
-            echo 'releases=["jammy","noble","questing","resolute"]' >> $GITHUB_OUTPUT
-            echo "Auto: building jammy, noble, questing and resolute"
+            echo 'releases=["jammy","noble","resolute"]' >> $GITHUB_OUTPUT
+            echo "Auto: building jammy, noble and resolute"
           fi
 
   build-and-upload:
@@ -136,7 +135,6 @@ jobs:
           case "${{ matrix.ubuntu_release }}" in
             jammy) RUST_VERSION=1.89 ;;
             noble) RUST_VERSION=1.89 ;;
-            questing) RUST_VERSION=1.88 ;;
             resolute) RUST_VERSION=1.91 ;;
             *) echo "::error::Unknown release ${{ matrix.ubuntu_release }} - add it to the case statement"; exit 1 ;;
           esac
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0d7bf47..8658bf4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Removed
+- **Ubuntu 25.10 (Questing) PPA**: the series reached end of life and
+  Launchpad rejects new uploads for it, so the PPA build matrix and install
+  docs drop it. Already-published questing packages stay in the PPA archive
+
 ## [1.6.0] - 2026-08-20
 
 ### Added
diff --git a/INSTALL.md b/INSTALL.md
index 2b8af1e..44d81af 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -99,7 +99,6 @@ The easiest way to install RustNet on Ubuntu and its derivatives is via the offi
 
 - Ubuntu 22.04 LTS (Jammy Jellyfish)
 - Ubuntu 24.04 LTS (Noble Numbat)
-- Ubuntu 25.10 (Questing Quokka)
 - Ubuntu 26.04 LTS (Resolute Raccoon)
 
 Derivatives register PPAs under their Ubuntu base series, so the same commands work there:
diff --git a/INSTALL.zh-CN.md b/INSTALL.zh-CN.md
index 3061235..a980355 100644
--- a/INSTALL.zh-CN.md
+++ b/INSTALL.zh-CN.md
@@ -99,7 +99,6 @@ choco install rustnet
 
 - Ubuntu 22.04 LTS（Jammy Jellyfish）
 - Ubuntu 24.04 LTS（Noble Numbat）
-- Ubuntu 25.10（Questing Quokka）
 - Ubuntu 26.04 LTS（Resolute Raccoon）
 
 衍生发行版会将 PPA 注册到对应的 Ubuntu 基础系列，因此相同的命令同样适用：
diff --git a/debian/README.md b/debian/README.md
index de49a9e..2e1c322 100644
--- a/debian/README.md
+++ b/debian/README.md
@@ -15,10 +15,9 @@ This automatically builds and uploads source packages for all supported Ubuntu s
 
 - Ubuntu 22.04 LTS (Jammy Jellyfish)
 - Ubuntu 24.04 LTS (Noble Numbat)
-- Ubuntu 25.10 (Questing Quokka)
 - Ubuntu 26.04 LTS (Resolute Raccoon)
 
-Each series ships versioned `rustc`/`cargo` packages satisfying the Rust 1.88 minimum required for the let-chains feature used by the project (see `rust-version` in `Cargo.toml`). The workflow pins the toolchain per series (Jammy: 1.89, Noble: 1.89, Questing: 1.88, Resolute: 1.91).
+Each series ships versioned `rustc`/`cargo` packages satisfying the Rust 1.88 minimum required for the let-chains feature used by the project (see `rust-version` in `Cargo.toml`). The workflow pins the toolchain per series (Jammy: 1.89, Noble: 1.89, Resolute: 1.91).
 
 ## GitHub Secrets Setup
 
@@ -56,7 +55,7 @@ sudo apt install rustnet
 - **Binary**: rustnet
 - **Maintainer**: Marco Cadetg <cadetg@gmail.com>
 - **PPA**: https://launchpad.net/~domcyrus/+archive/ubuntu/rustnet
-- **Supported**: Ubuntu 22.04 LTS (Jammy), 24.04 LTS (Noble), 25.10 (Questing) and 26.04 LTS (Resolute)
+- **Supported**: Ubuntu 22.04 LTS (Jammy), 24.04 LTS (Noble) and 26.04 LTS (Resolute)
 - **Architectures**: amd64, arm64, armhf
 
 ## Workflow