I'm wondering where these people might have bank accounts? It is pretty hard to function without one. Where are they registered for drivers licenses? Vehicle and trailer registration? Could any of those not be used to support location for residency?
It's actually the other way around -- In the US, one needs to declare domicile and THEN get voter registration, driver's license
, vehicle registration and insurance.
One needs a mail address and a physical address, the mail is usually a UPS Store mail box with bulk forwarding per phone call. The physical address depends on the state requirements.
Escapees in Texas will furnish both (and no state income tax) -- Voting rights there were challenged in court and upheld.
Banking accounts are not a problem in today's internet world and yesterday's 1-800 world -- Even now, my 'bank' is a credit union in Florida and I am domiciled and currently living in Washington state.