There's a dependency problem for deb-multimedia on Stretch, I believe
it was already solved in Buster as per another email. I believe the
version number needs to be changed from 1:1.10.4-dmo2 to 1.10.4-dmo2
for both gstreamer1.0-plugins-bad and libgstreamer-plugins-bad1.0-0.
libwebkit2gtk-4.0-37 : Depends: libgstreamer-plugins-bad1.0-0 (<
1.10.5) but 1:1.10.4-dmo2 is to be installed
$ apt-cache policy gstreamer1.0-plugins-bad libgstreamer-plugins-bad1.0-0
gstreamer1.0-plugins-bad:
Installed: 1.10.4-1
Candidate: 1:1.10.4-dmo2
Version table:
1:1.10.4-dmo2 650
650 http://www.deb-multimedia.org stretch/main amd64 Packages
1.12.4-2+b1 550
550 http://deb.debian.org/debian sid/main amd64 Packages
*** 1.10.4-1 650
650 http://deb.debian.org/debian stretch/main amd64 Packages
100 /var/lib/dpkg/status
libgstreamer-plugins-bad1.0-0:
Installed: 1.10.4-1
Candidate: 1:1.10.4-dmo2
Version table:
1:1.10.4-dmo2 650
650 http://www.deb-multimedia.org stretch/main amd64 Packages
1.12.4-2+b1 550
550 http://deb.debian.org/debian sid/main amd64 Packages
*** 1.10.4-1 650
650 http://deb.debian.org/debian stretch/main amd64 Packages
100 /var/lib/dpkg/status