Hmm... this is too funny to not to mention it here.

After exporting contacts using vcardconverter, I also exported the entire database of calls and SMS messages from old Jolla phone (now without SIM) to Xperia X.

First, export message groups and phone calls lists to a binary file: log in via ssh on Jolla and execute:
then move that binary file to Xperia X and execute:
[code]
commhistory-tool import ./mystuff
[code]
(you can safely ignore the bunch of warnings).

and everything gets in place and sorted by date, no UTF8 characters lost, added to the already existing recent calls and SMS text messages in its database.