Taxes in prison

My exhusband is in federal prison- he's had two different power of attorneys (his sister and his mom) and both have refused to file his taxes from 2021/2022. He recently asked if he could sign over PoA to me so I could file for him. This is tempting bc most of the income tax refund he'd get would come to me for back child support.

However, as little as I DO know, it seems like having power of attorney could potentially be a lot more complicated and involved if anything ever happened to him.

Aren't there organizations that can do this for him? Is a PoA doing it the only way?