I went through much agony to get this one. The first step is NOT obvious. I feel like I could’ve wasted the rest of my life trying to figure out the first method to apply for decryption.
But, as people have been saying, this one is related to another crypto challenge and a misc challenge. Indeed, can’t say much more without giving too much away. But if you PM me for hints, I’ll try to respond in a timely manner.