Currently it serves 2 apps. To add it to your F-Droid app, scan the QR code (click it to enlarge) or use this link:

https://submarine.strangled.net/fdroid/repo

If you would like to manually verify the fingerprint (SHA-256) of the repository signing key, here it is:
3D B2 D0 9F 57 32 45 E0 05 B6 A5 4E B5 EB F6 E6 A3 51 D6 A5 16 1C FE EF F1 44 2C 93 95 97 C3 1B