Where does the data in Peak Leads come from, and is it GDPR compliant?

Only from public sources: the LEI register GLEIF and Wikidata (both open data under CC0) and the company's legal notice (Impressum), which it must publish under § 5 DDG. Peak only reads pages that robots.txt allows, no social networks and nothing behind a login. Nothing is stored until you take over a lead, and then with source, link and retrieval date for each detail. The legal basis is the legitimate interest in initiating B2B business (Art. 6(1)(f) GDPR).