Finally got around to working on this again. A friend lent me a Windows machine with a USB-A port and it worked immediately as it should. I was able to see the helios64 machines boot.
Machine A (in use so far): Disconnected after starting the kernel.
Machine B (my backup unit): worked flawlessly.
I took machine B home with me and I'm setting it up as I want it. It's running bookworm with OMV7 now as desired.
Next time at the offsite location, I am going to take the HDDs from machine A and insert them into machine B. It's a software RAID that I set up via OMV at the time. I believe I should be able to just mount it in machine B and then set up all the services as they were before (more or less).
Then I'll take machine A back with me and see if I can figure out what was wrong with it. I think a new thread will be in order then because the solution was to use a machine with a USB-A port. The use of adapters seems to have been the reason why 'screen' kept malfunctioning. Whether or not it could also be an issue with the OS (i.e. macOS not working well with it), I don't know but I doubt.
Carlos Hartmann's post in Helios-64 Fails to boot since upgrading to Bookworm was marked as the answer