Steps to reproduce:

1. install the server with UI by intruction https://www.zabbix.com/download?zabbix=5.0&os_distribution=ubuntu&os_version=20.04&components=server_frontend_agent&db=mysql&ws=nginx
2.  open http://zabbix.server/ 

Result:
See screenshot...

Expected:
Configuration wizard of zabbix UI have to be shown

I have installed by instruction to a new VPS

Ubuntu 20.04.5 LTS (GNU/Linux 5.4.0-135-generic x86_64)

1. wget https://repo.zabbix.com/zabbix/5.0/ubuntu/pool/main/z/zabbix-release/zabbix-release_5.0-1%2Bfocal_all.deb
2. dpkg -i zabbix-release_5.0-1+focal_all.deb
3. apt update

x32 distribution has been used. for x64 not all packages was avalible, but that already mentioned in https://support.zabbix.com/browse/ZBX-21648