There are multiple people experiencing this bug, there are 2 threads in the forum with at least 4 people experiencing it, across multiple Debian-based operating systems (Ubuntu and Raspbian). See links below to forum threads. Possible solution has also been found, see below or in the forum threads

Steps to reproduce:

1. Follow upgrade procedure to upgrade from Zabbix 5.0 LTS to 5.4
2. Upgrade result = all OK, all components updated correctly
3. Web interface shows

   "The Zabbix database version does not match current requirements. Your database version: 5030069. Required version: 5040000. Please contact your system administrator."

1. Checking the zabbix_server.log gives the following

Unsupported DB! MariaDB version is 50505 which is smaller than minimum of 100037
current database version (mandatory/optional): 05030069/05030069
required mandatory version: 05040000
starting automatic database upgrade
[Z3005] query failed: [1832] Cannot change column 'scriptid': used in a foreign key constraint 'c_opcommand_2' [alter table opcommand modify `scriptid` bigint unsigned not null]
database upgrade failed

Additional information
Someone suggested to run "show columns from zabbix.opcommand;" which has the following result for someone experiencing this issue

MariaDB [(none)]> show columns from zabbix.opcommand;
+-------------+---------------------+------+-----+---------+-------+
| Field       | Type                | Null | Key | Default | Extra |
+-------------+---------------------+------+-----+---------+-------+
| operationid | bigint(20) unsigned | NO   | PRI | NULL    |       |
| scriptid    | bigint(20) unsigned | YES  | MUL | NULL    |       |
+-------------+---------------------+------+-----+---------+-------+

And should show the following for someone not experiencing this issue

MariaDB [(none)]> show columns from zabbix.opcommand;
+-------------+---------------------+------+-----+---------+-------+
| Field       | Type                | Null | Key | Default | Extra |
+-------------+---------------------+------+-----+---------+-------+
| operationid | bigint(20) unsigned | NO   | PRI | NULL    |       |
| scriptid    | bigint(20) unsigned | NO   | MUL | NULL    |       |
+-------------+---------------------+------+-----+---------+-------+

So the 'Null' column is different, for someone experiencing this issue it is 'null allowed' while for someone not experiencing this issue it is 'null not allowed'

Our database architect suggested that the database upgrade script doesn't drop foreign key 'c_opcommand_2' before editing the column and that they need to be dropped and re-added. This is confirmed so far by one user who manually dropped the foreign key using the following procedure, after which the problem was solved for him. I am going to try this on Tuesday and suspect it will solve my problem as well

ALTER TABLE zabbix.opcommand DROP FOREIGN KEY c_opcommand_2;
ALTER TABLE `opcommand` CHANGE `scriptid` `scriptid` BIGINT(20) UNSIGNED NOT NULL;
ALTER TABLE `opcommand` ADD CONSTRAINT `c_opcommand_2` FOREIGN KEY (`scriptid`) REFERENCES `scripts`(`scriptid`) ON DELETE RESTRICT ON UPDATE RESTRICT;

So this is almost certainly a bug with the database update script and because it happened to 4 different people at least across 2 different operating systems, more people will run into this without a doubt. If you need more information don't hesitate to contact me on my email

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Links to forum threads discussing this
First thread
Second thread