They won't.
What Ukrainian troops? Russians reported Ukrainians troops surrendering weeks ago when they initially invaded. This was was the case with the flagship Sahaidachyi, but it’s still Ukrainian. Whole lot of Russian BS.
But, news from reliable sources are not good either. Many troops have resigned or surrendered. They’re short on supplies and some are claiming they’re not getting clear orders from the leadership. There were evacuation plans but they’re still in their bases.