I believe the problem of secession was settled back in 1861-1865 by war, and a Supreme Court ruling in 1869 that NO STATE can secede from the US.
Texas v. White
1869 U.S. Supreme Court case ruling Civil War secession invalid
https://www.britannica.com/event/Texas-v-White
https://www.law.cornell.edu/supremecourt/text/74/700
So the Supreme Court’ has said but to me the relevant principle is stated in the Declaration of Independence, and no court can overrule that.
Opinions vary. But one thing is clear: a constitutional convention or amendement could rewrite all the rules, and allow for splitting up the country.
Whether it is the sane states leaving or kicking out the dysfunctional ones, it’s time for a divorce.
“Sanctuary state.” A mini-secession. How’s that? Hey, it’s a living Constitution now.