It's switch to the Euro or break the Good Friday Agreement.
For better or worse, Brexit has happened.
I wish it hadn't, but it has and we're living in that new reality.
The terms of the withdrawal agreement are what they are, and can't be changed in any significant way for the next five years.
Labour have made it clear that it won't make rejoining the EU part of its manifesto and, as Sid has suggested, the EU wouldn't welcome an application for readmission -- it's not going to happen in the next ten or fifteen years, at least.
In the meantime, life has to go on, and everyone has to adjust to the new reality, just as we're adjusting to the world of Covid-19 and solve problems as best we can -- it's no longer London vs Brussels, but the EU and Britain trying to resolve, or not, particular issues of mutual concern that are causing problems to both EU and British businesses and citizens.
ETA: Meanwhile
Swift action by both UK government and Brussels urged to deal with major problems
www.theguardian.com
Presumably this causes difficulty and inconvenience for their EU customers, who can certainly find alternative suppliers in most cases, but who presumably don't want to have to.