Coverage of BioWare's internal development issues over the past few years and the flawed games they have caused has invariably mentioned Frost engine issues. Since the engine wasn't really a good fit for developing RPGs, the BioWare development process became slow, and sometimes had to rebuild some of the most basic development tools.
We've covered the next Mass Effect engine many times before, based on EA and BioWare job ads. What further confirmed the matter is the official release of BioWare.
Recently, BioWare producer Brenon Holmes publicly announced a new recruiting position, Programmer, asking for UE4/UE5 experience, "Come and join our team in developing the new Mass Effect." This is the first time it has been officially confirmed that the new Mass Effect will use the Unreal 4/Unreal Engine 5.
The previous Mass Effect trilogy was developed using Unreal Engine 3, but then BioWare was forced to use DICE's Frost engine to develop Dragon Age: Judgment, Mass Effect: Andromeda, and Anthem, but all faced various development problems. Interestingly, the upcoming Dragon Age 4 also features a Frost engine.