Had you read the links you would see they address the study
The paper focuses on three states out of 50, and the authors say it’s wrong to generalize from this small sample. In fact, in another academic paper, the same authors found that in Iowa, Maine and Rhode Island, the most common registration for discharged felons was not to affiliate with any party.
"Ex-felons’ partisan affiliations vary across states, and we don’t think there’s enough evidence to claim that the national ex-felon population is ‘overwhelmingly Democratic,’ at least in terms of party registration," the authors told us.
But that isn't the narrative you want, is it?