We know there were gentile priests prior to the establishment of the Kohens. Melchizedek is an example.
In Shemot 19, there are two verses that refer to "priests" prior to the giving of the Torah.
Verse 22 – "And also, the priests who go near to the Lord shall prepare themselves, lest the Lord wreak destruction upon them."
Verse 24 – "But the Lord said to him, 'Go, descend, and [then] you shall ascend, and Aaron with you, but the priests and the populace shall not break [their formation] to ascend to the Lord, lest He wreak destruction upon them.'"
Who are these "priests" being referred to? Aaron was the first Kohen but wasn't installed as Kohen Gadol until later on after Mattan Torah. These priests could not be Kohens so were they gentile priests? Is this a translation issue with the English word priest?