I’m sure they’ll explain more as the show goes on, but if you pay close attention to the clues they’ve been dropping, the timeline makes perfect sense.
Chakotay goes out on the maiden voyage post-Voyager, around 2381 or 82. Chakotay goes through an unstable time anomaly and is sent 50 years forward in time, lands in a post-apocalyptic Solum where the Protostar is captured, loaded with a future Trojan horse weapon, then sent back in time through the same time anomaly but gets lost, landing a little too far in the past. The Diviner follows, spends years searching for it, creates Gwyndala, keeps searching until Dal and Rok discover it by accident in 2383.