Yes, it's possible. Viability depends on the details of how technical you are and how much trust you're willing to place in others. As far as spending goes, bitcoin transactions are quite small so the old joke is that you could send them via smoke signals.

On the receiving end, Blockstream setup a satellite to make it possible to stay in sync with the blockchain without internet access.

If you have periodic internet access you can get and save utxo set information and then use that to build your spends.

The other 34% of the world may not have net access but they have phones or know someone who does. In those cases they'll need to trust someone to interact with the bitcoin or lightning network on their behalf but this is much easier to do than to establish banking relationships when many countries are totally cut off. In the end Bitcoin is global and enables through minimal trust for everyone to join the global economy.

Already asked /answered similar here: #181484