For community-made plugins not included in the stock build, you can download the plugin folder and manually drop it into your device's internal storage directory under koreader/plugins/ .
For third-party plugins not included in the stock build, you can manually download the plugin folder and drop it directly into the koreader/plugins/ directory on your device's internal storage via a file manager or USB connection. Final Thoughts best koreader plugins top
Syncs your saved web articles directly to your device. For community-made plugins not included in the stock