Cook county jail is one of the few places that actually has voting centers in jails, so pre-trial detainees can vote.
Colorado to its credit adopted a law to have voting centers in all its jails. Likewise Los Angeles county has voting centers at its jails.
Maine, Vermont, and DC actually even let people in prison vote by absentee, including convicted felons, as prisoners in these jurisdictions never lose their right to vote.
But most jurisdictions are really bad about this. They don't provide the resources for people in jail to vote.
In Mississippi, over 11% of their population- and 16% of their black adults- are barred from ever voting even when they are released from prison due to past convictions.