Following the directions at https://www.zabbix.com/documentation.../debian_ubuntu to upgrade from 4.4.8 to 5.0, the upgrade fails with:

 
2065:20200513:154215.139 current database version (mandatory/optional): 04050074/04050074
2065:20200513:154215.139 required mandatory version: 05000000
2065:20200513:154215.139 starting automatic database upgrade
2065:20200513:154215.139 [Z3005] query failed: [1091] Can't DROP 'dropdown_first_entry'; check that column/key exists [alter table config drop column dropdown_first_entry]
2065:20200513:154215.139 database upgrade failed