B2B Link Building

Anybody can please share with me some free B2B backlink websites with quality DA, PA and low spam score

While not specifically B2B there are loads of guides to getting free backlinks posted on the forum. Just have a look around using the search function and some keywords like 'guide'. Then tailor your content to whatever aspect of B2B you are interested in to build up that topical relevancy. Some examples here:
https://www.blackhatworld.com/seo/m...eloper-grade-backlink-from-apple-com.1460524/https://www.blackhatworld.com/seo/guide-contextual-do-follow-links-on-caramellaapp-com.1466609/https://www.blackhatworld.com/seo/d...-backlink-method-step-by-step-method.1430241/