BG3 is NOT canon. WotC has repeatedly said over the years that anything from D&D video games is explicitly NOT cannon. Only WotC-released printed source materials are canon.
Yeah, I guarantee you this follow up to Descent into Avernus is canon. Gortash is canon. Astarion is canon. Orpheus is canon.
The only question is which direction will be canon. Did Astarion ascend or not? Those are the type of things up for discussion when it comes to canon.
Denial doesn't change what we all know to be true. This is a big part of the Forgotten Realms setting now.