[Update]
I have done some more debugging and found that it is probably a kernel bug.
It seems as if any kernel prior to 5.8 works but 5.8 and newer does not.
I have therefore, by using git bisect, found this commit that seems to be the root cause of my problem.
When manually reverting this commit on a kernel which prior to patching did not work, i.e. suspending made the computer freeze, the patched version works just fine.
I have started a conversation with the maintainer of the iommu subsystem to further investigate a possible fix to this issue.
/L