To follow up on this thread, and to leave an answer for future visitors, here is how it definitely works :D

First of all, as irknowles already mentioned, it is not sufficient to embed the server certificate, but you need the root certificate (which is also present in the certificate chain). This ...

I was trying to use nvs encryption with pre-generated data on the ESP-WROOM-32 using the Partition Generator Utility .
My ESP-IDF version is release/v3.3.

It drove me nuts that it didnt't work although I did exactly what the documentation says. It will always give me an error
0x1102 Id namespace ...