fakruzaruret in this request, Flarum is making a request to the PATCH endpoint of api/discussions/<id>.
That request is done by sending a POST request together with a X-HTTP-Method-Override: PATCH header.
If you get a 405 error, I suspect that X-HTTP-Method-Override has been removed by a proxy or server configuration. This could be a rule in your Apache rewrite, or something different along the path of the request.
Finding at what point that header is removed might not be easy. First step would be to check in the browser network console whether the header is sent with the request. If it's indeed sent, then the issue must be server-side. You should check the apache/nginx configuration for an obvious rule that might remove headers from requests.
If there is multiple level of proxying, like Cloudflare, apache behind nginx, or the opposite, you might need to increase logging at different steps to see where the header stops being present.
If you haven't already, you could also try disabling other third-party extensions to see whether one of them is causing the issue.
