diff --git a/.gitea/workflows/build.yml b/.gitea/workflows/build.yml
index 815777a8d..c289c6de4 100644
--- a/.gitea/workflows/build.yml
+++ b/.gitea/workflows/build.yml
@@ -1144,39 +1144,25 @@ jobs:
           echo "$result" >> "$GITHUB_OUTPUT"
           echo "decision: $result"
 
-      - name: install build-deps (sans ffmpeg — see [marfrit] step)
+      - name: install build-deps
         if: steps.skip-check.outputs.skip != '1'
         run: |
           set -e
           retry() { for i in 1 2 3; do "$@" && return 0; rc=$?; echo "retry $i (exit=$rc)" >&2; sleep $((i*5)); done; return 1; }
-          # Do NOT pull stock 'ffmpeg' here: the arch-aarch64 runner has
-          # ffmpeg-v4l2-request-fourier pre-installed from the mpv-aarch64
-          # job (configured via [marfrit]), and pacman -S ffmpeg would
-          # conflict on the libav* drop-in.  Daedalus build only needs
-          # libavcodec/libavformat headers, which the fourier package
-          # already supplies.  Keep cmake/ninja/pkgconf/libdrm here; the
-          # ffmpeg-dev equivalent comes via the next step.
-          retry pacman -Syu --noconfirm --needed \
-            dpkg openssh rsync curl base-devel git cmake ninja pkgconf \
-            libdrm
-
-      - name: ensure ffmpeg-v4l2-request-fourier installed (link-time ABI source)
-        if: steps.skip-check.outputs.skip != '1'
-        run: |
-          set -e
-          # Idempotent: pre-install the marfrit fourier ffmpeg so cmake
-          # finds libavcodec / libavformat / libavutil headers + .so's.
-          # Mirrors mpv-fourier-debian's [marfrit] step.
-          curl -sLo /tmp/marfrit.gpg https://packages.reauktion.de/marfrit.gpg
-          pacman-key --add /tmp/marfrit.gpg
-          pacman-key --lsign-key 92D5E96D8F63C75E4116AA1FF5C8C4603D0D250C
-          rm -f /tmp/marfrit.gpg
-          if ! grep -q '^\[marfrit\]' /etc/pacman.conf; then
-            printf '\n[marfrit]\nServer = https://packages.reauktion.de/arch/$arch\nSigLevel = Required\n' >> /etc/pacman.conf
-          fi
-          pacman -Sy --noconfirm
-          rm -f /var/cache/pacman/pkg/ffmpeg-v4l2-request-fourier-*-aarch64.pkg.tar.*
-          printf 'y\ny\ny\n' | pacman -S --needed marfrit/ffmpeg-v4l2-request-fourier
+          export DEBIAN_FRONTEND=noninteractive
+          retry apt-get update -qq
+          # libav*-dev provide the headers daedalus daemon dlopens at
+          # runtime — Debian's stock packages match the trixie ABI the
+          # daemon will encounter on Pi 5 hosts (both ship libavcodec
+          # 61.x).  The fourier ffmpeg fork isn't needed here; the
+          # daemon never link-binds against libav (Option γ — dlopen
+          # at runtime), so any header set with the right struct
+          # definitions works.
+          retry apt-get install -y --no-install-recommends \
+              build-essential cmake ninja-build pkg-config git \
+              libavcodec-dev libavformat-dev libavutil-dev libdrm-dev \
+              linux-libc-dev \
+              curl ca-certificates openssh-client rsync dpkg-dev
 
       - name: install hertz deploy ssh key
         if: steps.skip-check.outputs.skip != '1'
@@ -1238,7 +1224,10 @@ jobs:
         run: |
           set -e
           retry() { for i in 1 2 3; do "$@" && return 0; rc=$?; echo "retry $i (exit=$rc)" >&2; sleep $((i*5)); done; return 1; }
-          retry pacman -Syu --noconfirm --needed dpkg openssh rsync curl tar gzip
+          export DEBIAN_FRONTEND=noninteractive
+          retry apt-get update -qq
+          retry apt-get install -y --no-install-recommends \
+              dpkg-dev openssh-client rsync curl ca-certificates tar gzip
 
       - name: install hertz deploy ssh key
         if: steps.skip-check.outputs.skip != '1'