There seem to the following logical possibilities still:
The UK remains in the EU
The UK stays in a negotiated customs union with the EU, at least as regards goods
There is a customs border in Ireland
There is a customs border 'in the North Sea'
'Irexit', the Republic also leaves the EU
The customs union, or ability of the EU to impose standards on imported goods, is ended
The Republic won't agree to 3 or 5, the EU27 won't agree to 6, the DUP won't agree to 4, the Conservative Party apparently can't agree on 2, and if it's not 1 or 2, the UK has to decide where its customs border is. 1 seems unlikely without a change of UK government or second referendum.
One suspects the UK Government is now planning for 3, but doesn't want to admit it yet. I would hope that wouldn't lead to resurgence of war in Ireland just based on ordinary people having too much to lose, but then as ever the ordinary people aren't in control. I would have thought the 'backstop' proposal is a safer route to 4, with or without reunification.
