Hi !

After upgrading from Zabbix 5.2 to 5.4 succefully (I checked the prerequisites before, and no problems during update), a warning persist at every reboot of zabbix-server service :

2418:20210531:122520.290 Zabbix Server stopped. Zabbix 5.4.0 (revision 5059e20a75).
235439:20210531:122520.322 Starting Zabbix Server. Zabbix 5.4.0 (revision 5059e20a75).
235439:20210531:122520.322 ****** Enabled features ******
235439:20210531:122520.322 SNMP monitoring: YES
235439:20210531:122520.322 IPMI monitoring: YES
235439:20210531:122520.322 Web monitoring: YES
235439:20210531:122520.322 VMware monitoring: YES
235439:20210531:122520.322 SMTP authentication: YES
235439:20210531:122520.322 ODBC: YES
235439:20210531:122520.322 SSH support: YES
235439:20210531:122520.322 IPv6 support: YES
235439:20210531:122520.322 TLS support: YES
235439:20210531:122520.322 ******************************
235439:20210531:122520.322 using configuration file: /etc/zabbix/zabbix_server.conf
235439:20210531:122520.329 Unsupported DB! MariaDB version is 50505 which is smaller than minimum of 100037
235439:20210531:122520.330 current database version (mandatory/optional): 05040000/05040000
235439:20210531:122520.330 required mandatory version: 05040000
235439:20210531:122520.344 server #0 started [main process]

....

With loglevel 4 :

49800:20210531:132137.708 In zbx_dbms_version_extract()
49800:20210531:132137.708 MariaDB fork detected
49800:20210531:132137.708 Unsupported DB! MariaDB version is 50505 which is smaller than minimum of 100037
49800:20210531:132137.708 End of zbx_dbms_version_extract() version:50505
49800:20210531:132137.708 In DBcheck_version()
49800:20210531:132137.708 In DBconnect() flag:0
49800:20210531:132137.709 End of DBconnect():0
49800:20210531:132137.709 query [txnlev:0] [show tables like 'dbversion']
49800:20210531:132137.709 query [txnlev:0] [select mandatory,optional from dbversion]
49800:20210531:132137.709 current database version (mandatory/optional): 05040000/05040000
49800:20210531:132137.709 required mandatory version: 05040000
49800:20210531:132137.709 End of DBcheck_version():SUCCEED
49800:20210531:132137.709 In DBflush_version_requirements()
49800:20210531:132137.709 In DBconnect() flag:0
49800:20210531:132137.710 End of DBconnect():0
49800:20210531:132137.710 query without transaction detected
49800:20210531:132137.710 query [txnlev:0] [update config set dbversion_status='[\{"database":"MariaDB","current_version":"5.05.05","min_version":"10.00.37","max_version":"10.05.x","flag":1}]']

It looks like ZBX-19400 but i've not ProxySQL and my banner is clean :

Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 211441
Server version: 10.5.10-MariaDB-1:10.5.10+maria~bionic mariadb.org binary distribution

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

And MariaDB version :
mysql -e 'SELECT VERSION();'
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I repeat that all services are working properly and this problem is not blocking.

Regards
Romain.