Do you gain the benefit of the rogue's Reliable Talent feature if the roll is replaced with Portent?

Question

Here's what each class features says:

Reliable Talent

Whenever you make an ability check that lets you add your proficiency bonus, you can treat a d20 roll of 9 or lower as a 10.

and

Portent

When you finish a long rest, roll two d20s and record the numbers rolled. You can replace any attack roll, saving throw, or ability check made by you or a creature that you can see with one of these foretelling rolls. You must choose to do so before the roll, and you can replace a roll in this way only once per turn.

How do these features interact if a roll is replaced with a Portent die of less than 10?

Answer 1

There is no reason Reliable Talent cannot affect foretelling rolls

Something to note first is that Portent replaces only the d20 roll, not the entire result. Because of this, the roll would still be one that "lets you add your proficiency bonus", so we know that requirement for using Reliable Talent is still met.

The scenario would be that you are about to make an ability check, when a Divination wizard uses Portent to declare your d20 roll to be, say, a 5. You are still making an ability check and Reliable Talent lets you "treat a d20 roll of 9 or lower as a 10". In this case, the d20 roll is a 5 and I can see no reason Reliable Talent wouldn't increase this to a 10.

---

A potential sticking point is the fact that Reliable Talent states:

[...] you can treat a d20 roll of 9 or lower as a 10. [...]

So one might wonder whether Portent's die still counts as "a d20 roll" at all. The rules never actually define the phrase "a d20 roll" so we're be left looking to natural language where I would say Portent certainly counts as a d20 roll. The feature even states "roll two d20s" and calls these "foretelling rolls" which I would consider good enough evidence that the a Portent die is indeed a d20 roll.