If you only want to watch it once, renting Prometheus on Amazon costs roughly $3.99 USD. No pop-up ads, no viruses, no court summons.
The film is available through legitimate retailers like Movies Anywhere , where pricing and licensing terms are clearly defined. Prometheus EXPLAINED - Movie Review (SPOILERS) Vegamovies Prometheus
Prometheus was meant to be the start of a new trilogy. While Alien: Covenant followed, the third film was cancelled due to mixed reception and, notably, poor box office revenue. If you only want to watch it once,