While there (obviously) isn’t official confirmation on this, the site confidently stands behind their source.
BEGIN POTENTIAL PLOT SPOILERS
There’s a scene which takes place at the United Nations building, where government officials, civilians and protestors are discussing mutant rights (this part was previously confirmed by set photo leaks). According to the site, Professor Xavier and Magneto are in attendance, along with Jean Grey and Cyclops, who are surprised by the arrival of alien ships that launch an attack.
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The source says there were actors on set wearing motion-capture suits and they were clearly specified to be Skrulls.
There are a few more specific details which you can read over at the site (use their Google Translate function to read in English).
The inclusion of the Skrulls species is possible as 20th Century Fox shares those rights with Marvel Studios. Their are some specific Skrull characters that are licensed to each studio though. For instance, Fox can use Super Skrulls, while Marvel legally cannot. It’s complicated, but the alien race has been associated with the X-Men and Fantastic Four comics, so Fox has every right to use them if they wish.
If the Skrulls play a role, then what of the Shi’ar? The alien empire plays an extremely important role in the “Dark Phoenix Saga” comic storyline, but have they been replaced? Will they share the screen? The original comic storyline has a couple Skrulls. Actress Jessica Chastain already confirmed that she is not playing Shi’ar empress Lilandra, a character important to the comic plot. So is she playing a different Shi’ar character like Deathbird or a Skrull empress? Only time will tell.
We’ll find out eventually when “Dark Phoenix” flies into theaters on November 2, 2018.
Source: Universo X-Men