I’ve done some testing on our side,
It could be a issue with the theme, as the option seems to be completely removed.
I’ll have to bring this to the attention of the developer.
I can’t provide an update to when this issue will be addressed however.
You can keep tabs on the issue here and follow up if you wish.
The “See More” button’s URL will be the blog page’s URL by default.
In order to create a blog page you need to create a page and after that go to Settings -> Reading and select that page for Posts Page. If you will do this the blog URL from the homepage section will automatically point to that blog page. ( The option for a custom URL is exists in older version of the theme, but not with the new version of the theme. )