Create Global Regular expression, to "Return False" in case of:

Zabbix Agent
Microsoft\-Windows\-Perflib

Create item key:

eventlog[Application,,"Warning|Error|Critical",@ApplicationExcludeSource]

With zabbix_server 5.0.21 it works fine - (it ignored 2 sources)
With zabbix_server 6.0.2 the agent fails to retrieve the list of all active checks, hence all active checks stops working. Agent log file says:

2022/03/23 13:47:09.193256 [102] cannot parse list of active checks from [zabbix.contoso.lan:16051]: invalid tag "exp_delimiter" value ""

Attaching agent log with DebugLevel=5 which is linked to 5.0.21 (zabbix.contoso.lan:15051) and 6.0.2 (zabbix.contoso.lan:16051) at the same time.
zabbix_agent2.log