First need create the repo:

nano /etc/yum.repos.d/maria.repo

And past the repo info:

# MariaDB 10.3 CentOS repository list - created 2019-07-30 21:01 UTC
# http://downloads.mariadb.org/mariadb/repositories/
[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.3/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

After that time to make the upgrade:

yum update -y

And fix the issues, takes after upgrade steps:
mv /etc/my.cnf /etc/my.cnf.back; mv /etc/my.cnf.rpmnew /etc/my.cnf
service mariadb restart;systemctl status mariadb.service -l
mysql_upgrade
service mariadb restart;systemctl status mariadb.service -l

systemctl disable named.service;\
systemctl disable mysql.service;\
systemctl enable pdns.service;\
systemctl enable mariadb.service;\
ln -sv /usr/local/mgr5 /panel;\
ln -sv /usr/share/spamassassin /etc/spamassassin;\
mkdir /etc/old.mysql-configs; cp -pRv /etc/my.cnf* /etc/old.mysql-configs/

Where to check:
whmapi1 domainuserdata domain=somedomain.com
grep -Rl somedomain.com /var/cpanel/users/
grep -Rl somedomain.com /var/cpanel/userdata/
grep -Rl www.somedomain.com /etc/apache2/
grep -Rl somedomain.com /etc/*domains

After that:
/scripts/updateuserdomains
/scripts/updateuserdatacache
/scripts/rebuildhttpdconf
/scripts/restartsrv_httpd

quick fix:
chown root:root /usr/local/cpanel/whostmgr/docroot/cgi/softaculous/bin/soft
chmod 4555 /usr/local/cpanel/whostmgr/docroot/cgi/softaculous/bin/soft