In my experience while discussing with people in Zabbix telegram channel there are  some kind of people who misses a step of installation DBMS software for Zabbix Server or Proxy. I mean a steps like:

1. Add repository
2. Update package manager cache
3. Run install command (apt install <package-name>/yum install <package-name>/dnf install <package-name>)

In spire of it'a very obviously step, I think it will be good enchantment for newbies if Zabbix Documentation will has a links to MySQL, PosgreSQL etc web site with installation instructions or a section with simple steps like in list above.