So like, a CMS?

Use Ghost

Wordpress and Drupal seem to be the most popular. I like both depending on the website.

Wordpress, as mentioned, should cover you for most things, but you have to realise that Wordpress is getting more and more commercialised every day and cheap hosting is probably worse than a bad wordpress site. You can search for free plugins and theme inside wordpress for example, but if you really want to go white label then you will need to look at your own themes or modifying one to suit

I’m not sure if I understand completely correctly what white label websites are, but also maybe the themes made for the Hugo website building program?