How can I get taxa relative abundances from HUMAnN?

I’ve created a custom database for HUMAnN and I’m having trouble replicating the database with the same organisms in Metaphlan because many of the taxa don’t have genome representatives.

What would be the best way to use the output or intermediate files of HUMAnN to create something close to relative abundances? Could I just group by species and sum? I understand this will not be as robust as Metaphlan but can somebody walk me through some of the options I have using just HUMAnN?