Complex sentence: When Ukraine regained its independence from the Soviet Union, the castle was planned to be revamped and made into a presidential residence, but later an it was placed under the jurisdiction of the Lviv Arts Gallery.
Split into simpler sentences: When Ukraine regained its independence from the Soviet Union, the castle was planned to be revamped and made into a presidential residence. This never came to be, and eventually it was placed under the jurisdiction of the Lviv Arts Gallery.