For Journals using the OJS platform, there is a plugin (OJS Connector for the OpenAIRE Graph) which ensures compatibility with the latest version of the OpenAIRE guidelines for Literature, institutional, and thematic Repositories (OpenAIRE 4.0 guidelines). It's available at https://github.com/munipress/openAIREstandard and supports the current three major OJS versions 3.2.1, 3.3 and 3.
When the base OAI-PMH URL is available, you can proceed with the validation of your metadata by entering the details in the interface of your account in the PROVIDE Dashboard (https://provide.openaire.eu/), namely the OAI-PMH base URL and the desired compatibility (in your case the OpenAIRE Guidelines v4).
You can find more details about the OJS Connector for the OpenAIRE Graph at https://zenodo.org/records/12633203.