Is the lore in the video game Baldur's Gate 3 canon?
The story in the game can play out differently depending on choices you make, so anything related to that obviously isn't canon. But is e.g. Orpheus, the son of Gith, a canon character?
Until future official works come out confirming, or contradicting, the things seen in the game, its canon status is kind of presumptive. They might plan on treating it as canon now, but drop those plans in the future. They might not currently consider themselves beholden to treat it as canon, but wind up incorporating it into canon later. Until they do one or the other, any such plans are subject to change. (Frankly, even afterward, they might still change, but then they would have to ret-con.)
Anyway, that said, Wizards of the Coast hasn’t had said much publicly on what their plans are, fluid or otherwise. There is this interview, in which Mike Mearls says
There’s even some part we were working on in terms of the lore, that’s going to be coming back from the game to the sort of core of D&D, that might influence future tabletop stories.
This seems to imply that they are thinking of one particular thing as becoming canon—which might imply that they are not planning on incorporating the rest. For what it’s worth, that’s pretty consistent with how the previous games have been treated: they have not become D&D canon in general, but particular elements, such as Minsc and Boo, have become canon eventually.
Of course, Baldur’s Gate 3 most likely will be canon to any Baldur’s Gate 4 that gets released.
Murder in Baldur's Gate treats much of Baldur's Gate I and Baldur's Gate II as canon, so there is a precedence for Baldur's Gate III to work its way into official Forgotten Realms lore. Coran and Adrien Abdel are important NPCs in Murder in Baldur's Gate with the plot of the computer games included in their background. The adventure even plays a prank on player expectations by making the magic shop Sorcerous Sundries mostly a fraud (MiBG p55).
Now Blackhand earns a large, steady income from the import and sale of components for rituals and spellcasting, dubious fortune-telling, and even-more-dubious spells of good luck or greater skill. Blackhand flatly refuses to sell spells, and he denies having magic items for sale. However, to keeps the rumors alive and his prices high, the wizard sends his apprentice, a gnome named Gilligunn, to contact seekers of such items and make transactions “away from the master’s eye.”
Murder in Baldur’s Gate is written by Ed Greenwood which makes it canon unless specifically contradicted by the current owner of D&D. QED Ed's inclusion of material from the video games makes that material canon.