Hello everyone!
After 2 weeks of hard work, I’m finally finished, tuned and secured (A+ level by ssllabs.com) my new NxC_18 fresh installation on Centos 8. After switching my home family new environment to production all seams to be fine except an PHP error logged: “The behavior of unparenthesized expressions containing both ‘.’ and ‘+’/’-’ will change in PHP 8: ‘+’/’-’ will take a higher precedence at /var/www/html/nextcloud/3rdparty/sabre/vobject/lib/Recur/RRuleIterator.php#423”.
Does anyone can help me to understand a solve in order to have an “Error free home production system”? 
The configuration summary following described:
OS: CentOS 8 (4.18.0-147.8.1.el8_1.x86_64)
Nextcloud 18.0.4
PHP: Version: 7.4.6
MySQL (Mariadb) 10.3.17
Many thanks in advance, regards.
Jeev@an