I don't think that's possible with searxng (but I'm not 100% sure, but I can't seem to find that feature)
I know there are browser extensions which can filter out domains in search results for different search engines like google and duckduckgo.
But the pinning/lowering/raising is a bit trickier to implement as an extension, because what kagi does is basically:
- Load 3 pages of search results in the backend
- Show a result as the first entry if it matches a rule for pinning
- Influence the search ranking algorithm with the lower/raise rules of the user
- Filter out blocked domains
It would be possible but not as "streamlined" as Kagi does.
Don't get me wrong, Kagi definitely has its rough edges and the search ranking algorithm is sometimes very unpredictable, but it provides good enough results for me to be worth the 10$ per month for unlimited searches.
I'd recommend using GrapheneOS. (i'm using it, and it is a breath of fresh air)