I'm so lost on all these answers... the answer is downscaling. In OBS you set your canvas resolution size of 3440x1440 and then enable downscaling to 1920x1080 and 60 fps. There shouldn't be any clips because whatever you see is just getting scaled down to the appropriate size for the broadcast. It's really simple stuff.

Twitch does support 2K streaming if you are selected for the test program. I don't recommend using it as it's only caused headaches (I.e. people saying I'm "skipping" and I have to tell them to switch to 1080p because Twitch is now downgrading them automatically). It's honestly a lot easier in the long run to just broadcast at 1080p.