diff --git a/deps/CMakeLists.txt b/deps/CMakeLists.txt
index a6a4187c9f..967f47aac2 100644
--- a/deps/CMakeLists.txt
+++ b/deps/CMakeLists.txt
@@ -238,7 +238,7 @@ if (NOT IS_CROSS_COMPILE OR NOT APPLE)
                 DEPENDEES download # do after download
                 COMMENT "Freeing Space: Removing source archive"
                 WORKING_DIRECTORY ${DEP_DOWNLOAD_DIR}
-                COMMAND ${CMAKE_COMMAND} -E rm -r ${projectname}
+                COMMAND ${CMAKE_COMMAND} -E rm -rf ${projectname}
         )
         ExternalProject_Add_Step(dep_${projectname} free_build_space
                 DEPENDEES install # do after install
diff --git a/deps/DataChannel/DataChannel.cmake b/deps/DataChannel/DataChannel.cmake
index 50d49a7148..23c256b365 100644
--- a/deps/DataChannel/DataChannel.cmake
+++ b/deps/DataChannel/DataChannel.cmake
@@ -1,6 +1,25 @@
 # libdatachannel is the native ICE/DTLS/SCTP implementation used by the
 # GUI WebRTC camera controller. Keep the source revision fixed: the signaling
 # protocol is evolving independently of this transport dependency.
+#
+# It vendors plog, usrsctp and libjuice as git submodules, which a plain
+# GitHub tag tarball does not include. The flatpak sandbox has no network
+# access during the build, so there the manifest itself clones the repo
+# (submodules and all) straight into this ExternalProject's default source
+# dir before the sandbox closes; with no download method given here and that
+# dir already non-empty, ExternalProject_Add silently uses it as-is instead
+# of trying its own (network) git step.
+if (FLATPAK)
+    set(_datachannel_source "")
+else()
+    set(_datachannel_source
+        GIT_REPOSITORY https://github.com/paullouisageneau/libdatachannel.git
+        GIT_TAG v0.24.5
+        GIT_SHALLOW ON
+        GIT_SUBMODULES_RECURSE ON
+    )
+endif()
+
 orcaslicer_add_cmake_project(DataChannel
     DEPENDS ${OPENSSL_PKG}
     CMAKE_ARGS
@@ -13,8 +32,5 @@ orcaslicer_add_cmake_project(DataChannel
         -DUSE_SYSTEM_USRSCTP=OFF
         -DOPENSSL_ROOT_DIR:PATH=${DESTDIR}
         -DOPENSSL_USE_STATIC_LIBS=ON
-    GIT_REPOSITORY https://github.com/paullouisageneau/libdatachannel.git
-    GIT_TAG v0.24.5
-    GIT_SHALLOW ON
-    GIT_SUBMODULES_RECURSE ON
+    ${_datachannel_source}
 )
diff --git a/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml b/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml
index 6d6029c6b2..e6aa25d88c 100644
--- a/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml
+++ b/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml
@@ -326,9 +326,15 @@ modules:
         dest: external-packages/FFMPEG
 
       # libdatachannel v0.24.5
-      - type: file
-        url: https://github.com/paullouisageneau/libdatachannel/archive/refs/tags/v0.24.5.tar.gz
-        sha256: 454537c3cd526bed935d847bb2dff4046f266eef84d43b2a5f2f2f293c0026f4
+      # Use git instead of archive: it vendors plog, usrsctp and libjuice as
+      # git submodules, which a plain GitHub tag tarball does not include.
+      # Cloned (with submodules) straight into the ExternalProject source dir
+      # that deps/DataChannel/DataChannel.cmake expects, since the sandboxed
+      # build step has no network to do this itself.
+      - type: git
+        url: https://github.com/paullouisageneau/libdatachannel.git
+        tag: v0.24.5
+        commit: 443f6934d9007eb7076ab7825ba330f355fcbead
         dest: deps/build_flatpak/dep_DataChannel-prefix/src/dep_DataChannel
 
       # ---------------------------------------------------------------