I nearly fell for their $6-for-the-first-year Business Plan account. Whups! Good thing I asked some questions first.
The sales person answered the chat after approx 20 mins, and was not customer friendly. When I enquired about included CPanel apps, I was abruptly told that CPanel is not included - you must purchase it separately. She did not tell me (this is what I mean by "abrupt"), but I read elsewhere, that they wrote their own "CPanel-like" administration tool - but from what I can tell it is significantly less capable. And as of this writing, I still do not know if they offer Node.js (which was something that I asked the sales rep but she did not answer).
I would be interested to see a screenshot of the IONOS CPanel replacement. I also would like to know what included apps they offer, such as phpBB, SimpleMachinesForum, Node.js, Python, Ruby - and how Git management/deployment works. As of this writing, and over 30 minutes on chat with them (including wait time), I have no idea.
Here is a fairly recently article from Dec 2021 that sheds more light:
https://websitesetup.org/hosting-reviews/ionos/