discover is not bad for searching for flatpaks
But as a software center for the system it is not (yet) mature enough.
In solus SC I am shown 1.2 GiB.
eopk shows this too.
but discover only 333 MiB and errors on top of that.
So long story short, manage the system via eopk cli and flatpak cli.
Search and explore packages via solus SC and discover