Answer from taglib,
Hi Ton,

As far as I know, DSDIFF/DSF was never part of an official TagLib release.

It was merged into master (2018-10-27, d71398c9), but it was later
removed (2019-09-12, 074f30e3) with the commit message

Remove DSF and DSDIFF from master to a feature branch

These can be merged back into master once they're in a more mature state.

@Scott: Can you tell us what exactly were the problems which led to
this removal?

The code still exists in the taglib2 branch. It is not difficult to
include support for a new tag format in a project which is using
TagLib, that code does not have to be part of TagLib, so the
Strawberry Musicplayer could add DSF support to its source code. I did
this myself for, but I used
another implementation from
(2015-03-11, 18687eb2), and I had to add a few fixes based on bug
reports from users, so an alternative to the stuff in the taglib2
branch could be the src/plugins/taglibmetadata/taglibext/dsf folder in
the Kid3 sources.

Jonas, was this helpful?