myQNAPcloud SSL certificate used with web serveur

[Mac2luxe]

Hello everyone,
I have a Qnap TS-251 + on which I activated the web server to host 2 sites, I try to pass the connection in https using myQNAPcloud SSL certificate, however when I want to buy the certificate in question this message of warning appears:

Please note that myQNAPcloud SSL Certificates can only be used with the myQNAPcloud DDNS domain name. Your certificate will be associated with your QNAP ID with which you are currently logged in and can not be switched to another account.

suddenly I wonder; my domains like "tralala.com" and "tralala.fr" will not be able to work in https with a SSL certificate myQNAPcloud? This will only work with a domain like "tralala.myqnapcloud.com" is that it?

thank you all

[thomas_janotta]

Yes, as far as I understand this certifacte. Only my myqnapcloud.com
I guess you have to use let's encrypt, which maybe can configured for such domains...