Ceasefire agreement and a return to negotiations would be a start. They had already agreed to a deal when Boris Johnson showed up over a year ago though, and then Ukraine went back on it after his unscheduled visit. My assumption is that this agreement would have preserved Donetsk and Luhansk as either independent countries or as autonomously governed regions of Ukraine, that's changed now with the law making them part of Russia and I'm not entirely sure whether that's something Putin even has the power to change without a vote by those respective regions or the State Duma (unsure what mechanism might exist).

Either way there is no military capability to take them back by force as demonstrated by the complete failure of the counteroffensive, Ukraine will either lose them by force with a massive pile of bodies lost on both sides, or not. This is the reality of the situation. I care about avoiding the pile of bodies one way or another.