I assume, that the themes on the publii website are official
so are there any other themes that we can use for this CMS?
I have not seen any. There may be some somewhere. I just have not found them yet.
As I grow more comfortable with developing themes, I want to convert a few more HTML5UP templates and perhaps create a few myself using Coffeecup Site Designer. I am making some custom templates for a few sites as we speak.
For what it is worth, Publii is absolutely amazing. So much so, I am converting some of my sites using my own CMS to use Publii and will be creating more sites using Publii. I will be donating soon!