How to report on an academically required internship with a bad supervisor relationship
If the jury asks about my appreciation of the company where I did the internship: should I be honest in telling them what happened and that my advisor is too incompetent? Or should I lie and tell them everything was fine?


You should do the same as in any other case when a professional relationship goes wrong. You need to:


Focus on the facts. "The project was not going smoothly" is a fact. "We had communication issues, so I ended up delivering not what they wanted"  is also ok. "The project was going badly because the advisor is incompetent" is you trying to assign blame. Stay clear of that. You do not need to lie to the committee and pretend that all was great, but try to refrain from presenting your own interpretation of the events. It is understandable that you will want to make sure that the committee understands that the issues were due to no fault of yours, but by badmouthing your advisor (no matter how warranted) you are likely to reach the opposite.
Take the high road. If it is customary that students write an acknowledgement to their advisors, write a short, polite acknowledgement thanking him to allow you to  work in his team, if you can thank him for nothing else. Rocking the boat over something so minor seems unwise.
Whatever you do, stay professional. Acting out of anger and a lust to "get back" on your advisor for his insults will backfire on you.


Important Edit:

Based on your follow-up information:

(retracted - some racist comments as well as statements about unduly long work hours)

The fourth, maybe even more important point is:

If something really bad went on (like in your case), find out what the correct official action to take is. File an official complaint with your university, or even talk to a lawyer and have him look into filing a law suite (racist comments in the workspace are certainly grounds for a civil law suite where I live). Don't take a placebo action that does not hurt and does not help, such as not including him in your acknowledgements.

The other 3 points stay in place - even if something terrible went down, you need to stay professional and you need to focus on the facts, in your official reports as much as when you talk to your jury about the incident(s).