Hi,
The MediaRecorder element does not place any constraints over transfer, it is the browser that requires CORS validation when sending a POST request from one domain (farm.pcibex.net) to a different domain (where your server is hosted). It could be that you somehow overrode the certificate’s invalidity in your instance of Firefox, but other browsers will just refuse to proceed with the POST request in the absence of a valid certificate
It is possible to use a self-signed certificate, but you’ll likely run into issues like the one you describe here. If possible, I recommend using certbot to automatically get letsencrypt certificates, which won’t necessitate manual approval
Jeremy