Few suggestions shared below:
1. Do manual link building
2. Particularly from .edu , .gov sites
3. BTW you don't require thousands of backlinks for microniches
4. PBNs work for fast ranking as said by another respondent. Just a few days
5. I have access to a low-cost PNB and use it for some of my sites
6. If you want to know how to make PBN check amazon kindle, Udemy
7. Several fulltime internet marketers make their own PBN