One screen is a 32 inch UHD 60Hz monitor and the other one is a 24 inch 2560x1440 90Hz screen which is rotated by 90 degrees.
OSX refuses to support it because it eats into their monitor sales that use an alternative TB-based multiplexing protocol (which is only available on Apple devices, which are, well, not the world's best monitors, yet somehow the most expensive per square inch in a lot of cases).
All the various incarnations as far back as Ivy Bridge's TB2 should have working support in Windows and Linux. I have physically tested it on my MBPR from that era, and it worked, and I know of other people's newer OS-swapped Macs also working.
Lack of MST support in OSX has historically blocked 4k early adopters: 4k screens exported themselves as two logical displays due to 4k monitors coming out ahead of HBR2-capable controllers.
As for ARM-era Macs, as far as I know, they licensed a common ASIC block for their DisplayPort transceiver, which is also what AMD, Nvidia, and Intel have done. So, their hardware should still support it fine, but I have no clue if Asahi's work on the GPU driver has gotten MST to work.
It's ridiculous that they refuse to support this. Iit's actually backfiring. Peoppe at work laugh when they see me attaching two cables to my Macbook ehile everyone else with different operating systems use their docking stations or daisy chaining. Even old Chromebooks support it.
My records indicate it is this: https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-u...
I drive two 34UM88 with it.