If I had my 'druthers, disenfranchisement for felonies is anti-democratic nonsense, so people in prison should retain voting rights.
The only ethically-hard problem is which jurisdiction their vote should count in, since they cannot demonstrate it by choosing where to live. Perhaps a choice between:
1. The location of the prison, if their main interest is the conditions of their detention rather than anything outside.
2. The location of their property or close family, because they're still paying property-taxes or school levies etc. and they will be returning there later.
The only ethically-hard problem is which jurisdiction their vote should count in, since they cannot demonstrate it by choosing where to live. Perhaps a choice between:
1. The location of the prison, if their main interest is the conditions of their detention rather than anything outside.
2. The location of their property or close family, because they're still paying property-taxes or school levies etc. and they will be returning there later.