Messy desk at the moment but wanted to see if the latest developer preview will have my iPad work on my 49 inch ultra-wide display and it does! Not perfect, but I'm glad this is finally getting somewhere!
It was working for me on the ultrawide 3440x1440 (you have the super ultrawide, or the ultra-ultrawide?) but I had to change the scaling from more space to zoomed for it to work on DB1. Now on DB2 there is no option to adjust the scaling but it works just as it did on DB1.
Also why does your scaling look so terrible, everything looks so big?