I don't know if there's a full list, but here's my shot at it:
- Two new maps, Detachment and Argyle
- Forge Beta
- File Share available in menu, with Forge creations and "343 recommended" list
- Ranked Updates that change how you gain and lose CSR
- Sandbox updates, including buffs to the plasma carbine, commando and plasma pistol. A nerf to the battle rifle
- Campaign Co-op (online), with new achievements and mission replay
- Match XP beta, which changes the match to match progression through the battle pass
- QoL updates, including a reduction of weekly challenges
- 30-tier battle pass for the Winter Update
- Playlist changes, including a shift to "core" and "rotational" playlists, and a new mode, Covert One Flag
- Further sandbox updates, like a change to meleeing with the Sword
- Further networking updates, like an improvement to reduce ghost melees
- The Pit, an official re-imagining, entering matchmaking
- A december event, The Winter Contigency, with an event pass and a new mode