@ Dr. Mouse
"The solutions I have seen so far have either been rejected by Hard Brexiteers or Loyalist parties in NI"
Really? Like what? I know the negotiators made a number of suggestions and the EU rejected them then suggest they annex Ireland.
"or depend on coming up with some magical new technology/systems in a very short space of time."
Magic technology the EU is already considering implementing elsewhere in the EU.
"In short, there have been no realistic solutions put forward."
Since this is the EU's problem that is very disturbing. That would suggest that the EU, who's existence is predicated on being able to establish trade and improve relations in the world, is incapable of its task.
"We keep arguing round in circles, and we're obviously not going to agree here. I cannot see how the Irish border is not a problem of the UK's making for the UK to solve, and I also can't see how you would disagree."
You do seem to have identified the problem. How can the EU's border control be the UK's problem? Just as the EU has no say over UK controlled borders once we leave. So if our side decide no border that is it, our side implements no border. That doesnt dictate what the EU does but their border is their problem.
Interestingly apparently the smart people on both sides cant agree on what a hard border is-