DIM Destiny 2: What Still Works After the Final Update

Most DIM guides still quote a 600-slot vault and explain armor stat tiers that no longer exist. This one is current: vault transfers, loadouts, Armor 3.0 optimizing, the search filters worth memorizing, and a fix list for when DIM stops loading. Plus the question nobody else answers, which is whether any of it still works now that Destiny 2 has stopped receiving updates.