While the lure of "exclusive" forum links is high, the safest way to enjoy Office 2019 64-bits is through official channels. This ensures your data remains secure and your productivity tools stay updated.

Use a retail product key. Many legitimate retailers offer discounted one-time purchase keys that provide a lifetime "Full" license without the risks of third-party scripts. Conclusion

Using unauthorized activation methods violates Microsoft’s Terms of Service. How to Download and Activate Safely

Use the Microsoft Deployment Tool or your official Microsoft Account portal to download the genuine ISO.