Hey,
I know that CRIU generates dump and restore stats. But do LXD provide some stats after the migration? Like the size of the files that were transferred, the downtime.
Couldn’t find any info about this
sorry for the many questions in the last few days 
In theory you could use lxc monitor against the source and target, this should include periodic notification on how much data has been migrated and include detailed timestamps.
That may provide you with what you’re looking for, albeit not in the most convenient way to read.