See a discussion on hiding pages such as Photos and Archive at the Micro.blog Help Center — How can I hide (but not delete) core pages?:
Q: I want the photos & archive pages to exist, but not be visible in the blog category links.
A: Photos and Archives really should have that “Include this page” checkbox. I’ll work on adding that. In the meantime you will probably need to create a custom theme that overrides the header to just show the links you want instead of having Micro.blog manage it.
The discussion includes specific techniques.