Suprisingly i couldn't find any ppa with prebuilt ffmpeg packages to add QSV (intel quicksync video) support.
Are there any, around? And isn't QSV added by default because it would rely on proprietary code? What other reason could there be, since it's a feature that >50% of the systems have these days?
After some research, got the answer, hopefully useful for sbd else:
Most packages are already available in recent Ubuntus, the only missing one is a properly compiled ffmpeg. Simple instructions provided by Intel on github: https://github.com/Intel-Media-SDK/MediaSDK/wiki/Build-and-use-ffmpeg-with-MediaSDK
Note that to enable all codecs, default hardware-accelerated codec packages have to be replaced with non-free versions, as explained here: https://github.com/Intel-Media-SDK/MediaSDK/wiki/Intel-media-stack-on-Ubuntu