yup ! It worked ! Thanks
I had to adjust the instructions to opensuse tumbleweed, since the package chromium-ffmpeg-extra put the file libffmpeg on folder /usr/lib64/opera/lib_extra.
Besides that, its works on next run:

zypper in chromium-ffmpeg-extra
mv /usr/lib64/opera/libffmpeg.so /usr/lib64/opera/libffmpeg.so.obsolete
n -s /usr/lib64/opera/lib_extra/libffmpeg.so /usr/lib64/opera/libffmpeg.so