Yes, this should be possible but it won't be easy. Inside the CI module, there should be a SmartCard (looks kind of like a credit card) which you take out.
Next, you need to buy a SmartCard-reader. Everyone recommends Easymouse but those are discontinued so you have to find an alternative. I have a "Stinger Dual USB" which was a bit difficult to setup. The important thing is, that you need to be able to use it under Linux (or whatever operating system you're using).
Once that is set up, you can install OSCAM (https://fleet.linuxserver.io/image?name=linuxserver/oscam) which is a software that can interact with the SmartCard. For OSCAM to work, you need to have the so-called "boxkeys" (rsa keys for your card). This is the step that makes or breaks it. If your type card has been "cracked", the boxkeys will be leaked somewhere. Some cards (like Sky) have special mechanisms which make it virtually impossible to "crack" them. If this is the case, you can't use the card with TVHeadend.
If you manage to setup OSCAM, you can just add your OSCAM server in TVHeadend under "Configuration > CAs" and you'll be able to play encrypted channels.
The site https://www.digital-eliteboard.com is very helpful when it comes to this topic, but the forum is German and most discussions are Germany-specific.
If you have further question, feel free to ask, but I can't promise I'll know the answer.
