Nothing like it exists on the system. It looks like it may be a new package as it appears to be only available for Questing and Resolute.
KDE Neon 6.6.5
Since May 24th, there exists a symlink libMpvQt.so.3 - maybe haruna just needs a repackaging.
Just adding corresponding so.2 symlink does not work.
Fails on a symbol lookup.
Fixed with an update today.