I just got 2021 SP2. MacBook Pro with Catalina.
I always use dual dimensions. I have yet to start a new document, but i opened up a couple existing document and the imperial units have completely disappeared (as in this report) or they are stuck at whole numbers (even thou not and set to 1/32).
Metric units seem to work fine (doesn’t matter if metric or imperial are dominant).
I opened a 3rd document and i could not get it to screw up. All the originals are v2017
dave