Please let me know if you know how to migrate PST files to Thunderbird without using Outlook.. eSoftToos PST to MBOX Converter app is a practical alternative for converting PST to Thunderbird without Outlook migration issues. Just a few more steps are needed to complete it. Each folder in a PST file should be exported as a separate MBOX file. Both of our customers have access to a free trial version. You will try out the trial version for free.
Read more:- https://www.esofttools.com/pst-to-mbox-converter.html