LPR/DPR must go back to Ukraine.
That is non negotiable.
Crimea can be bargained.
Again, just my opinion.
If the West forces Ukraine to the peace/bargaining table without any prospect of regaining all of Ukraine and all of Crimea, the people of Ukraine will see that as one more betrayal like the Kurds, like the Afghanis. And they will hate the US implacability.
My 1 1/2 cents.
One of the peace plan options has Russia “leasing” Crimea from Ukraine.