I’m sure ‘commhistory’ has been discussed, have you searched here and also on together.jolla.com?
It’s in sqlite format:
$> file ~/.local/share/commhistory/commhistory.db
/home/defaultuser/.local/share/commhistory/commhistory.db: SQLite 3.x database, user version 4, last written using SQLite version 3037002, writer version 2, read version 2, file counter 79, database pages 80, cookie 0xe, schema 4, UTF-16 little endian, version-valid-for 79
There’s a command line tool that shows you everything in clear text:
commhistory-tool listgroups
Why is that not good enough? You want to import it back to your Android phone?