You can't for a simple reason: to use them you need a combination of hw, sw and connectivity that's largely proprietary and can't be considered safe... You may

You can't for a simple reason: to use them you need a combination of hw, sw and connectivity that's largely proprietary and can't be considered safe... You may trust your FOSS-only OS, your FOSS "wallet", but how you can trust your hw? How easy a country can look out citizens from internet services? Mesh network and open hardware exists but mostly at a marginal and embryonic stage...