Dragon Age: The Veilguard has three endings. Broadly and arguably too-simply, there’s a good ending, a neutral ending, and a bad ending. There’re a lot of choices that go into reaching these endings, but they all lead to one of these three:

The point of no return in Dragon Age: The Veilguard is during the 'When plans align' quest where you have a meeting with Morrigan. While you're having the meeting with Morrigan the end of the game will trigger and you'll be given a choice.

The Veilguard's best side quests arguably should have been a main story quest, due to what it reveals about the game's antagonist.