I also performed the upgrade using the complete version from the official source and I found the following error in my journal:
Oct 20 21:39:21 [hostname] roundcube: PHP Fatal error: Uncaught Error: Class 'Spoofchecker' not found in /var/www/webmail/program/lib/Roundcube/rcube_spoofchecker.php:50
#0 /var/www/webmail/program/actions/mail/index.php(1400): rcube_spoofchecker::check('gmail.com')
#1 /var/www/webmail/program/actions/mail/index.php(523): rcmail_action_mail_index::address_string('[removed]...', 3, false, NULL, 'utf-8')
#2 /var/www/webmail/program/actions/mail/list.php(123): rcmail_action_mail_index::js_message_list(Array, false, Array)
#3 /var/www/webmail/program/include/rcmail.php(275): rcmail_action_mail_list->run(Array)
#4 /var/www/webmail/index.php(283): rcmail->action_handler()
thrown in /var/www/webmail/program/lib/Roundcube/rcube_spoofchecker.php on line 50
The relevant part is:
Class 'Spoofchecker' not found
This closed issue report Uncaught Error: Class 'Spoofchecker' not found #8127 suggested that the package
php-intl is now a new requirement. This forum post gives more details:
According to https://bugs.php.net/bug.php?id=63790 the Spoofchecker is only available when PHP intl extension is built with ICU >= 4.2. So, I suspect your build does not have it, but it is required.
So it depends on your system, if
php-intl needs to be installed. On newer systems, it is not necessary.
php-intl depending on your system:
dnf install php-intl
apt install php-intl
Don't forget to restart your webserver.