Ok, thought I would just go and test it out
Did a search and replace on SHA512-CRYPT in /var/www/mail/inc/functions.inc.php and replaced it by SSHA256.
Then have every user change their password.
Next step is changing /etc/mailcow_version to 0.14_sogo
upgrade ./installer -u
After the upgrade,
usermod -a -G postdrop sogo
and restart postfix and sogo and it should work.