Does anyone know if there is a fix or a upcoming fix?

Just did a whole ton of searching for this today and found something that worked for me. Granted, I did this on a GTX 970 so not sure if it works as well with AMD cards. Playing on a LG 3440x1440 monitor with a fresh install and no mods (will update after if any mods break this for me.)

Using WIdescreen Fixer, use the settings cog for Witcher 2, select v.3.4.0 (GoG) if it isn't already, unselect Automatically Detect Aspect-Ratio and select Cinema (2.39:1) from the drop down menu.

Been playing for over an hour and haven't seen a black bar yet (except prerendered cutscenes.)

Hopefully this works for you.

I really wish Widescreen fixer worked. But the game crashes before i see the menu. I have a 2560 x 1080 so i set it to cinema mode. But no luck. I've tried everything.

After the v.3.5.0 update there is no solution anymore that works with the Witcher 2... Which is a huge bummer... I mean they just implemented it for Apple silicon, but you still cant play it on ultrawide monitors...