Ukraine: Territorial Concessions on the Negotiation Table?

International negotiations are underway regarding potential territorial concessions from Ukraine to Russia. According to CNN, Moscow has reportedly made "certain concessions" regarding five Ukrainian regions: Crimea, Luhansk, Donetsk, Zaporizhzhia, and Kherson.
The Financial Times, Bloomberg, and Reuters reported that Vladimir Putin proposed to Donald Trump to "freeze" military operations along the front line in exchange for Moscow's full control of the Donbas. This would imply ceding territories not fully controlled by the Russian army.
Ukrainian President Volodymyr Zelensky stated that Kyiv is ready to discuss territorial changes within the framework of a peace agreement but categorically ruled out the concession of territories not already under Russian occupation. European capitals are skeptical of any concession of Ukrainian territory.