Well, your processor actually does NOT support AVX2 which almost virtually guarantees that mine doesn't. So I guess I'm up a creek without a paddle.
I had a similar error message from DOS2 and could not play the game, until very recently. It seems like the devs might address this after release by having a game executable that can fall back on old instructions, though at a performance penalty. I suppose right now they're concentrating on performance rather than compatibility.
I would not count on it on though. You do have some options, but none of them are great. Probably the 'easiest' would be to get Boot Camp running Windows 10 on your Mac. If BG3 will run on my CPU under Windows, it's a sure thing that it will run on yours - with Windows, though.
You could also invest in a new Mac, or just get a gaming PC, though those options are cost-prohibitive. But I wouldn't wait around for the devs to sort this out - it's likely going to be a while, if ever.
