Yes: Ardour (DAW with built-in mastering tools), Calf Studio Gear (Linux/Win), and LSP Plugins (high-quality free suite). They require more manual work but are 100% free.
Some users assume that because Ozone 5 is over a decade old and iZotope no longer sells it directly (they sell Ozone 11), the software should now be free. This is a misconception. Abandonware is a legal grey area, but iZotope still holds the copyright. Distributing cracks or keygens is illegal. iZotope - Ozone 5 Advanced VST Free Download
Ozone 8, 9, 10, or 11 are included in the Music Production Suite. You won’t get Ozone 5 specifically, but you’ll get far superior algorithms. iZotope frequently runs sales where the suite is 50–70% off (e.g., $149–199 for Ozone 11 Standard). Yes: Ardour (DAW with built-in mastering tools), Calf