Yelnya is a delightful place! It's just a miracle! I highly recommend the guide Kasia Kazachenok. Kasia loves swamps, and they love her. You can listen to her endlessly. There is a boardwalk through the swamp (2.5 km). You can walk in sneakers, there are puddles, but they are surmountable. In certain places, you can walk through the swamp itself, and swim in the lake at the end of the trail. The water is clean. There are animal trails and observation towers. You can come by yourself, but it's better to book a guide in advance.
This is not a field for you to go to. Peace and quiet. Sometimes you can hear the birds flying by. Cool. But I can't get out of my head the idea of how to find the path back.