Oracle 18c is supported in PC 10.5 for Repository Service.
Check the below 10.5 PAM for more details:
PAM for Informatica Platform v10.5: PAM for Informatica Platform v10.5
Check under the sheet 'PCRS_MM' / 'PowerCenter Repository Servicec (PCRS) & Metadata Manager (MM)'.
Thanks, I know this. But what about exactly Express Edition version? Is this version supported too? Or are Standard/Enterprise Edition supported only?
Oracle Express Edition is not supported for Informatica because these kind of editions usually come with some limitations.
Please, refer to this KB for more information about it:
To add to David's response, the Oracle Express Edition is a lightweight client and is not a complete version of the client. This lacks a certain libraries used for OCI functionality by the application.
Hope this helps.
To add from a "practical" point of view, while it MAY work to create a repository using Oracle Express, usually at latest after reboot of the machine or a restart of the Informatica domain repository access will no (longer) work at all. That's just experience from 16 or 17 years since I've read about Oracle Express for the first time.