Gave it a shot on my laptop with RegataOS 24 (OpenSuSE Tumbleweed) running Kernel 6.8.2, and the Magewell driver did fail, but most likely another change since 6.5 is my guess. The most recent driver is from just over a year ago (3/10/2023), but the changelog mentions Kernel 6.1 and 6.2 in it. I'll l0ad up Ubuntu 23.10 as a live distro later, and test there (since it ships with 6.5).
[Edit]
I forgot to mention that if you send Magewell's support team the compilation logs, they tend to work out the error pretty quickly for a driver update. I'll reply/edit once I test on Mantic to see if 6.5 changed something.
[Edit 2]
Ok, so it does not compile on 6.5.0 in Mantic Minotaur (23.10). The current LTS (23.04 Lunar Lobster) does ship with Kernel 6.2. So that version ought to work.