Kdenlive
kdenlive.org
Free, open-source, non-linear video editor with multi-track editing, effects, and color grading — a full alternative to Premiere Pro.
Why it is useful
Kdenlive supports professional workflows like multi-track timelines, keyframeable effects, proxy editing for large footage, and a wide range of import/export formats, all without a subscription. It's actively maintained (KDE project) and capable enough for everything from YouTube editing to short-film production.