For the serious cinephile, the National Film Archive of India (NFAI) often showcases rare films. While they do not offer direct downloads, they are a primary source for film preservation, and many of their restored classics eventually make their way to official YouTube channels or film festivals.
YouTube is arguably the largest repository of Old Kannada movies on the internet. Many production houses and copyright holders have uploaded classic films to their official channels to generate ad revenue. You can find full-length movies starring legends like Dr. Rajkumar, Vishnuvardhan, and Shankar Nag, often for free. Download Old Kannada Movies
The first thing you must understand is the copyright status of these films. For the serious cinephile, the National Film Archive
Warning: Avoid websites offering "unlimited free downloads" of new-old classics. These sites are often honeypots for malware, ransomware, and surveillance. For the serious cinephile