Can Alert prevent Surprise if you don't know combat is occurring yet? [duplicate]

Question

If part of the party enters combat with enemies but the rest of the party is not aware of the threat or aware there is combat happening yet, does a player with the Alert feat who rolls highest on initiative act before even the enemies?

In this example, the Archer has the Alert feat but is hanging back behind a corner waiting for the Paladin to see if things are safe. The group rolls Initiative and the Archer rolls 21, the Spiders roll 15, and the Paladin rolls 8. The Spiders roll 24 for Stealth and Surprise the Paladin.

Who acts first? The only answers I come up with seem to unfairly negate the Archer's choice to take the Alert feat.

The relevant part of the Alert feat:

You can't be surprised while you are conscious.

Answer 1

The archer is not surprised and may act.

Surprise is a mechanic used to make sense of a particular narrative feature. It restricts what you are able to do on your turn in the initiative order, because narratively, you have been taken completely by surprise by your enemy.

So you take the alert feat - you are not mechanically restricted on your turn by being surprised, but your in-universe knowledge of the situation may or may not restrict what you would do.

So it comes down to roleplaying style. What does the ranger know about what is going on? What the archer does next is totally up to them. Do you act on player knowledge the character does not have? Do you play true to the narrative and act as though you have no idea combat has begun? That's a question for you and your players to discuss. But from a rules standpoint, the archer is not surprised and may take their turn.

Consistency of timing among a split party.

I would rule against rolling initiative only for the paladin and spiders because the timing of combat is quite precise - six seconds per round. I have to adjudicate the archer's actions in relation to the timing of the combat going on around the corner, and initiative is exactly how that is done. I want to maintain consistency in the timing of the archer's actions and the actions of the combat.