When Russia attempted to negotiate a ceasefire and a peace deal with Ukraine in March 2022 the proposal on the table was that Donetsk and Lugansk would remain independent. There was even a suggestion the Donbass rebels could eventually return to Ukrainian sovereignty, albeit with a very high degree of regional autonomy.
It was the failure of the Istanbul peace negotiations and the continuation of the war that made Russia’s annexation of the Donbass inevitable; same was true of Kherson and Zaporozhe.