diff --git a/.gitea/workflows/build.yml b/.gitea/workflows/build.yml
index c289c6de4..65128d2b5 100644
--- a/.gitea/workflows/build.yml
+++ b/.gitea/workflows/build.yml
@@ -924,11 +924,20 @@ 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 base-devel git nasm yasm \
-            linux-api-headers mesa alsa-lib bzip2 fontconfig fribidi gmp \
-            gnutls lame libass dav1d libdrm freetype2 libpulse libva \
-            libvorbis libvpx libwebp x264 x265 libxml2 opus v4l-utils xz zlib
+          export DEBIAN_FRONTEND=noninteractive
+          retry apt-get update -qq
+          # Debian build-deps for the FFmpeg fourier-fork build.  These
+          # map 1:1 to the previous Arch list; libav*-dev intentionally
+          # absent (we are FFmpeg itself, providing those libs).
+          retry apt-get install -y --no-install-recommends \
+              build-essential git pkg-config nasm yasm \
+              linux-libc-dev libgl1-mesa-dev libasound2-dev libbz2-dev \
+              libfontconfig-dev libfribidi-dev libgmp-dev libgnutls28-dev \
+              libmp3lame-dev libass-dev libdav1d-dev libdrm-dev \
+              libfreetype-dev libpulse-dev libva-dev libvorbis-dev libvpx-dev \
+              libwebp-dev libx264-dev libx265-dev libxml2-dev libopus-dev \
+              v4l-utils liblzma-dev zlib1g-dev \
+              curl ca-certificates openssh-client rsync dpkg-dev
 
       - name: install hertz deploy ssh key
         if: steps.skip-check.outputs.skip != '1'
@@ -1063,31 +1072,30 @@ 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 base-devel git meson ninja python-docutils \
-            ladspa wayland-protocols vulkan-headers \
-            alsa-lib desktop-file-utils glibc hicolor-icon-theme jack lcms2 \
-            libarchive libass libbluray libcdio libcdio-paranoia libdisplay-info \
-            libdrm libdvdnav libdvdread libegl libgl libglvnd libjpeg-turbo \
-            libplacebo libpulse libsixel libva libvdpau libx11 libxext \
-            libxkbcommon libxpresent libxrandr libxss libxv luajit mesa mujs \
-            libpipewire rubberband sdl2 openal uchardet vapoursynth \
-            vulkan-icd-loader wayland zlib
-
-      - name: configure [marfrit] repo + pre-install ffmpeg-v4l2-request-fourier
-        if: steps.skip-check.outputs.skip != '1'
-        run: |
-          set -e
-          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 marfrit/ffmpeg-v4l2-request-fourier
+          export DEBIAN_FRONTEND=noninteractive
+          retry apt-get update -qq
+          # Debian libav*-dev is ABI-compatible with the fourier ffmpeg
+          # fork at the header level; mpv link-binds against system
+          # libav at build time, runtime dlopen picks up the fourier
+          # libs if installed.  The previous [marfrit] pre-install of
+          # ffmpeg-v4l2-request-fourier under pacman is unnecessary
+          # under apt: stock Debian libav*-dev provides the trixie
+          # ABI mpv-fourier's binary will encounter.
+          retry apt-get install -y --no-install-recommends \
+              build-essential git meson ninja-build pkg-config python3-docutils \
+              ladspa-sdk wayland-protocols libvulkan-dev libwayland-dev \
+              libasound2-dev desktop-file-utils libc6-dev hicolor-icon-theme \
+              libjack-jackd2-dev liblcms2-dev libarchive-dev libass-dev \
+              libbluray-dev libcdio-dev libcdio-paranoia-dev libdisplay-info-dev \
+              libdrm-dev libdvdnav-dev libdvdread-dev libegl-dev libgl-dev \
+              libglvnd-dev libjpeg-dev libplacebo-dev libpulse-dev libsixel-dev \
+              libva-dev libvdpau-dev libx11-dev libxext-dev libxkbcommon-dev \
+              libxpresent-dev libxrandr-dev libxss-dev libxv-dev libluajit-5.1-dev \
+              libmujs-dev libpipewire-0.3-dev librubberband-dev libsdl2-dev \
+              libopenal-dev libuchardet-dev libvapoursynth-dev liblzma-dev \
+              libavcodec-dev libavformat-dev libavutil-dev libswscale-dev libswresample-dev \
+              zlib1g-dev \
+              curl ca-certificates openssh-client rsync dpkg-dev
 
       - name: install hertz deploy ssh key
         if: steps.skip-check.outputs.skip != '1'