2 unmarried people on a land contract, relationship ending. How can 1 person get their name off the land contract>

One buys the other out, ( basically a contract within the contract)

By using terms in the contract for one member to withdraw ( if there are any)

By agreement of both parties and the seller who would redo the contract ( normally for a fee)

One question that should be answered is what penalties does the contract have for breach. If the only penalty is loss of right to purchase the land, the leaving member can walk with impunity.