Importing FreeTube subscriptions to NewPipe/Tubular

In FreeTube, navigate to Settings > Data > Export Subscriptions > Export YouTube (.csv).

Transfer the csv file to your mobile device.

In NewPipe/Tubular, navigate to Subscriptions > upper-left triple-dot > Import from > YouTube > Import File > choose the csv file.

The import will run in the background with notification. The app’s notification will clear once the import is complete.