I am running the latest KDE Neon 5.16 and when running ffmpeg on the command line I receive this error:

ffmpeg: error while loading shared libraries: libsndio.so.7.0: cannot open shared object file: No such file or directory

It looks like the version that came installed with neon is libsndio.so.6.1

This happened on a freshly installed Neon.

ffmpeg available by default to install in Neon is 7:3.4.6-0ubuntu0.18.04.1 from the Ubuntu archive. This correctly links against libsndio.so.6.1 and runs ok.

libsndio.so.7.0 comes from a version of sndio (>= 1.4) that never existed in the Ubuntu repo for Bionic. Bionic has 1.1.

So it appears you are using a ffmpeg build on your system that was built against later versions of sndio than is available in the default Neon (Ubuntu base or Neon repos).

How did you install ffmpeg?