diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 8fe4dea85a..00b2e4e7fd 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -79,7 +79,7 @@ workflow:
   # Default Docker image (unless otherwise defined)
   image: debian:${DEB_VERSION}
   variables:
-    DEB_VERSION: "bookworm"
+    DEB_VERSION: "testing"
     # Common cloning procedure
     GIT_DEPTH: "1"
     GIT_SUBMODULE_STRATEGY: none
@@ -141,7 +141,6 @@ deps-debian:
     entrypoint: [""]
   variables:
     GIT_STRATEGY: none
-    UMFPACK: libumfpack5
     PKGCONF_RELOCATABLE_OPTION: '-Dpkgconfig.relocatable=true'
   script:
     - export container=docker
@@ -184,6 +183,7 @@ deps-debian:
             libaa1-dev
             libappstream-glib-dev
             libarchive-dev
+            libbacktrace-dev
             libbz2-dev
             libcfitsio-dev
             libgexiv2-dev
@@ -210,7 +210,7 @@ deps-debian:
             libspiro-dev
             libsuitesparse-dev
             libtiff-dev
-            $UMFPACK
+            libumfpack6
             libunwind-dev
             libwebp-dev
             libwmf-dev
diff --git a/build/linux/appimage/3_dist-gimp-goappimage.sh b/build/linux/appimage/3_dist-gimp-goappimage.sh
index ce5b5b9f46..ed05f810c4 100644
--- a/build/linux/appimage/3_dist-gimp-goappimage.sh
+++ b/build/linux/appimage/3_dist-gimp-goappimage.sh
@@ -345,8 +345,6 @@ if [ "$GIMP_UNSTABLE" ] || [ -z "$GIMP_RELEASE" ]; then
   bund_usr "$UNIX_PREFIX" "lib/libEGL*"
   bund_usr "$UNIX_PREFIX" "lib/libGL*"
   bund_usr "$UNIX_PREFIX" "lib/dri*"
-  #TODO: remove this on Debian Trixie (which have Mesa 24.2)
-  conf_app LIBGL_DRIVERS_PATH "${LIB_DIR}/${LIB_SUBDIR}dri"
 fi
 ### Debug dialog
 bund_usr "$GIMP_PREFIX" "bin/gimp-debug-tool*" --dest "libexec"
diff --git a/devel-docs/os-support.txt b/devel-docs/os-support.txt
index 60f7e73a1f..6a4910482b 100644
--- a/devel-docs/os-support.txt
+++ b/devel-docs/os-support.txt
@@ -9,11 +9,10 @@ developers maintaining GIMP for this platform will decide.
 
 ### GNU/Linux, *BSD…
 
-Until GIMP 3.0 release, Debian 12 "bookworm" stable will be our baseline target.
+From GIMP 3.4 release, Debian 13 "trixie" stable is our baseline target.
 I.e. that we can bump a minimum dependency version only if it is in Debian
 bookworm.
 
-After GIMP 3.0 release, we might get back to depend on Debian Testing.
 
 ### macOS