Let’s look at the big picture.
Blue hash is Kharkiv oblast, which Russia is supposedly abandoning entirely. Yellow is the parts of Luhansk Oblast Russia conquered since February. Open, empty, with few roads, Russia wasn’t able to hold it in the 2014 war. Not sure how strategic it is right now, and whether Ukraine will want to claw some of that back.
The pre-invasion Luhansk and Donbas border are clearly defensible, and that’s where Russia presumably will head. The green hash is the part of Kherson Oblast that Ukraine has cut off, with a heavy Russian presence suffering from poor-to-non-existent supply lines.
But what about the south? Reports a heavy Russian presence in the stretch between Mariupol and Melitopol, and Ukraine can’t cut those troops off. They can be resupplied easily via the Azov sea. Russia’s problem is that supply lines from there to Melitopol (and further west toward Kherson) are served by a single rail line, in the town of Tokmak.
Expect that place to start showing up soon, the way we always knew Kupiansk and Vovchansk would be keys to liberating Kherson Kharkiv. [It had been a while since I'd made that mistake...]