From this topic:
https://meta.discourse.org/t/searching-solved-posts/69648/5?u=bloomexperiment
Appending ?solved=no
to a topic list URL would show unsolved topics e.g.
https://forum.example.com/latest?solved=no
To add a navigation link amongst the Latest/Top buttons, you could use this theme component:
and use the URL with ?solved=no