Slack exports come in JSON, unles you are on the Enterprise-Grid plan. So there's lots of parsing to be done to make sense of it all.

The trick was in converting the epoch timestamp

Reference: https://stackoverflow.com/questions/45540191/json-convert-epoch-timestamp-jq-error-at-stdin-cannot-index-string-with

The trick is in parsing threads... TBD

This will go through sub-directories