Daryl, I've got an inquiry into the Yuma 2 engineers to get a few more details. However, I'll say that the testing we've done with the USB to Serial adapter (AG ACCAA-566) has all been done for the use of the Mobile Software with rate controllers and external GPS and we've verified it works in these scenarios. I can say from past experience that we've also had struggles supporting different third party USB to Serial adapters (primarily with laptops). Typically we found the issues dealt with missing drivers and such. For this reason, we are only supporting the AG ACCAA-566 adapter with the Yuma 2 and Mobile.
The Yuma 2 Product Manager has also suggested:
There is an accessory vendor, Portsmith Technologies, that has some very high performance adapters that may be useful for legacy connection methods. They have a USB to Ethernet adapter.