I too have used ISPConfig like @GrnEyedDvl and enjoyed it for a few years on my dedicated server. Ive recently switched to HestiaCP mainly because I switched server providers and it was a one click install lol. ISPConfig can be alittle confusing to get around at first but it’s very customizable, it would be the ideal control panel if you reselling hosting as you can create billable accounts for users, allocate certain amounts of resources to these users etc, much like a hosting provider.
Everything else is a Fisher Price server with big buttons. You'll never learn the finer details of how things actually work, or how to configure a forum better, cheaper and faster by compiling what you need and removing what you don't.