Adding the USB 2 card did nothing to help even though it was recognised in the bios.
Can you boot from the USB 2 card? I doubt it. I haven't seen a USB device, connected to a plug in USB card that shows up as a boot device. It certainly isn't impossible, but it is unlikely.
Some of the USB 2 ports are enabled using a USB 3 passthrough.
Is there an actual USB 2 adapter (other than what is on the plug in card)? If not, there is no way to connect those ports too a USB 2 adapter. It is possible, that they "work" because the BIOS is still driving the devices. I expect that the USB 2 card doesn't work until the USB 2 driver gets loaded, and initialized. That happens very late in the boot sequence.
I had to borrow a keyboard with a PS/2 plug to get everything up and working again
This is one of the main problems with using USB keyboards. They don't work after the BIOS loses control (sometime early in the boot sequence), and before the driver initializes (right at the end of the boot sequence). At that time, USB keyboards cannot be used to do simple things like hit <enter>. This is not new with new USB drivers, it has always been the case.
I will say again that ArcsOS does work, less USB 3, on a Ryzen machine if you use a working image from another AMD based machine (may need a 7th gen A series processor). So far I have been unable ti actually install from DVD or USB.
You should be able to install from DVD, but you may need to convince it to not use the UEFI boot method. That should be an option, somewhere in BIOS.
You can probably install from USB too, if you use a little trick:
Make two USB sticks, with the installer on them. Put one in a USB 3 port, which should boot (again, the UEFI boot isn't going to work), and load the MEMDISK, then ArcaOS can boot from the MEMDISK. At the end of that boot, the USB 3 port will not be usable, BUT, the USB 2 driver should be loaded, and the installer will find the rest of the installer on the stick that is in the USB 2 port (the plug in card, NOT the on board stuff). From that point, it should install normally.
Another way, is to make a small HDD volume (less than 2 GB, I use 2030 MB), and build the ArcaOS installer in that (it should be formatted FAT16). Boot from that volume, and you should be able to do the install (detailed instructions are in one of the README, or PDF, files in the root of the DVD). You may need to have Air Boot, or some other boot manager, installed, to be able to boot from the FAT16 volume.