Anyway, I have that same monitor. Why it won’t work with your MacBook Air? Black screen? Did you try set the DisplayPort version to 1.2 (or even 1.1)?
I posted about it here:
https://forums.macrumors.com/threads/49-chg90-qled-monitor-not-working-with-2014-air.2106422/
Basically, my Air is 2012 or 2013 model and cannot support that resolution. And what's more frustrating is I have a newer (2014) MacMini that has lower specs, but for some reason is able to support the resolution.
My MacMini is late 2014... 1.4 GHz Intel Core i5, with 4GB of RAM. (new screen works great via display port)
My MacBook Air is 2012 or 2013 (?)... 1.7 GHz Intel Core i7, with 8GB of RAM. (black screen via display port, but works with HDMI down-scaled to 1080p and stretched 2-wide)
So now I'm stuck with this big screen that I love.... but my "good" computer won't work with it... and the extra MacMini that I had runs slow as a dog on it. I even bought new 16gb of ram to stick into the Mini to try to speed it up, but didn't realized Apple prevented that with the 2014 model.
My old setup was using the Air with my Apple 27" Thunderbolt Display.... that's worked great for the past few years but I wanted more screen space for work/multi-tasking.
My thought was to just sell my Air, Mini, and TB display.... and roll it all into just a new MacBook Pro or a Mac Pro.... both ones in my 'shopping cart' are right at $3k... but the rumors are that both are at risk of being replaced/updated this year.
My first thought was for the new 15" MacBook Pro, but since as I said I'm 95% of the time just at my desk, I don't mind the idea of a tower if I'm getting higher specs for the same money.
The mid 5K i5-7600 iMac benches 5089 single 14869 multi £2219 with a 16gb ram upgrade and 256gb ssd to match the mac pro. You also get Thunderbolt 3 and a 5k display worth £1000.
The mac pro doesn't make sense, its old and its expensive.
The iMac isnt ideal, but neither is the mac pro its essentially the same set up without a screen. Granted you can upgrade the CPU but thunderbolt 3 allows better graphics cards down the line etc thunderbolt 2 is essentially now useless. Neither have good internal storage options so external raids are the way to go... I wouldn't want to spend essentially the same money for an older technology.
I am not interested in any iMac or iMac Pro as the whole point is I want to use the ultra-wide screen. I have Apple's 27" Thunderbolt Display now that I was using previously with my Air.