The EU is not changing its rules. All major trading blocs have tariff arrangements and customs controls. You can't expect the EU to bend its rules on account of one dissident country out of 28.

Fair enough. That is why the EU wish to impose a border. But one of their continuing members, the Republic of Ireland, does not want a border imposed.
UK has made it clear we will not be imposing a border.

How is this a UK problem. The EU are responsible for how they maintain their own borders (even if the Republic don't agree).
Why are the UK expected to sort it out?