Missing Package "gss-ffmpeg"?

System: Ubuntu 22.04, 64 bit, running in Oracle VirtualBox.

I wonder if someone can point me in the right direction. Trying to install some software that has a dependency on the "gss-ffmpeg" package. Running:

sudo apt install gss-ffmpeg

reports back the usual:

Reading package lists... DoneBuilding dependency tree... DoneReading state information... DonePackage gss-ffmpeg is not available, but is referred to by another package.This may mean that the package is missing, has been obsoleted, oris only available from another sourceE: Package 'gss-ffmpeg' has no installation candidate

If I run:

sudo apt install gss*

I see a line:

Note: selecting 'gss-ffmpeg' for glob 'gss*'

Which (I think) suggests that 'gss-ffmpeg' exists.

I have VM's setup for 18.04, 20.04 and 24.04 so I tried to install on each of those as a test. 20.04 and 24.04 give the same message, 18.04 doesn't find anything (tells me to add a repo).

Am I missing a repo somewhere? Any pointers?

Thanks in advance.