where do you read that DM900, or any other Dreambox is not working ?
Basically you can say, that all Linux-based receivers work (if a Oscam-version is available for your receiver or you can compile it on your own). I cannot find any post with "DMxxxx not working".
And as you have chosen: Newcamd-protocol is best for Oscam, with CCcam-protocol many users get rule violations shown in connection history or even by email, if configured. The required settings are available from the "my subscription" page regardless of the receiver you use.
You might have found information, that THE BOX (itself) is not supported. As you explained you need to go to something called Blue Panel etc - this is receiver specific, its completely different from installing an emulator on my receiver (Neutrino system, no so called "Panel" installed at all). But you cannot expect that every type of receiver is known here (even if Dreambox is well known - in Germany!), so best answer you can get is: contact a receiver-specific support-forum for "how to install/configure emulators" as the procedure is different on any type of box. Searching for "DM900" here in the forum discovers one thread regarding freezers - this is also "problem" for receiver-support in this case. Sometimes it will do to change to an older version of the emulator but as soon as it freezing while the server response time is fast enough (depending on used encryption, around 600ms for NDS or 6 seconds for Nagra, Cryptoworks, Conax for example), this has to be fixed from the builders of you receivers software (in your case Enigma), or from Oscam support (best to use Streamboard.tv but webpage is currently unavailable)