Realistically, your only option on these for data recovery is to get the board working again or replace the board through Apple. Which is quite pricey. The problem, as Dan mentioned, is that these are not really true SSDs. They do not contain a controller for the storage, so putting them into another iMac pro, or a USB adapter (which as far as I know was never made) would not work, because all of the data as to what information is stored where, is within the T2 chip on the logic board for the iMac.
It would be like looking at a map with no street names or designations for anything. All the data is still there, but there's no way for the machine to know what is what. And with the iMac Pro, there are 2 drives paired together, so there is the additional complication of that.
Depending on what is wrong with the logic board it may be an easy fix for someone who is competent at board level repairs, but I know there is not a lot of information available for those.