@JulienMAURIER-5459, Welcome to Microsoft Q&A! Thanks for posting the question and sharing the solution that worked for you.
For benefiting the community, summarizing the scenario:
Scenario: Unable to deploy Wordpress on Linux App Service WebApp.
Error: The deployment shows the following error.
{
"code": "DeploymentFailed",
"message": "At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.",
"details": [
{
"code": "Conflict",
"message": "{\r\n \"Code\": \"Conflict\",\r\n \"Message\": \"Parameter with name DATABASE_HOST already exists.\",\r\n \"Target\": null,\r\n \"Details\": [\r\n {\r\n \"Message\": \"Parameter with name DATABASE_HOST already exists.\"\r\n },\r\n {\r\n \"Code\": \"Conflict\"\r\n },\r\n {\r\n \"ErrorEntity\": {\r\n \"ExtendedCode\": \"01013\",\r\n \"MessageTemplate\": \"Parameter with name {0} already exists.\",\r\n \"Parameters\": [\r\n \"DATABASE_HOST\"\r\n ],\r\n \"Code\": \"Conflict\",\r\n \"Message\": \"Parameter with name DATABASE_HOST already exists.\"\r\n }\r\n }\r\n ],\r\n \"Innererror\": null\r\n}"
}
]
}
Typically, the error message may occur if you're using the database host name which already exists. In this case, use a different host/parameter name so there is no name conflict.
Solution that helped- "It was du to the portal app. I've tried in standard web browser and it worked :) " (Copied from the "Edit" on the post).