I personally use Debian. For your case, you can install lightweight desktop environments such as XFCE.

Honestly from my point of view after reading your post, you don’t have a terminal or operating system issue, it feels like you are new to self-hosting and don’t know how to start configuring from scratch.

Ideally you want to look for documentations or keep asking for online help. For example, with installing docker, you would want to refer to this: docs.docker.com/engine/install/. Welcome to system admin life, where you spend more time reading/understanding than configuring. Personally, you can even use AI Chatbot to help you with stuff, just be specific on the system you are on, the goal you are trying to achieve and the problem you are tring to solve.

Which brings me to answer your next point about CasaOS: It exists so that you can skip most of the ‘system admin life’ step