Harvey Smith, the creative director of Arkane Studios, confirmed that Redfall is not based on Unreal Engine 5as in a conversation with WCCFTech.
So yet, the issue had never been clarified with precision, and it was generally assumed that the new Arkane game would be among the first to utilize the Epic Games graphics engine in its entirety, but it isn't, according to reports.
Epic released Unreal Engine 5, although the game is based on Unreal Engine 4.26. If we had more time, we might have switched everything to Unreal Engine 5, but it took a lot of effort to upgrade to 4.26, according to Smith.
On the other hand, Arkane never suggested that this be a game for Unreal Engine 4.
On closer inspection, there is clearly mention of Unreal Engine 4 as the game's graphics engine, therefore it would not be a surprise revelation. In the meantime, Smith has released a sample of Redfall, and Microsoft has not yet cancelled a PS5 version.