Is it possible to block unlisted numbers with F-Secure's call blocker on Android? If so, how, and if not, will this ever be a feature?
With my small experience about Android device - there was (for me) temporary troubleview for such feature (kind of not possible to use) and it was helpful reinstallation F-Secure SAFE (and next re-login to account under device);
Or maybe if you by 'unlisted numbers' mean 'hidden numbers' (or something like that) - previously such features was missing with F-Secure SAFE (as their own feature) because there should be 'default' system ability/feature of Android platform (such as more good to use it). I did not check it with Android platform, but with my Windows Phone there indeed build-in system ability to block hidden numbers (not sure if Android platform should be with missing feature; at least recent Android versions);
Just as additional words to previous good reply - there can be useful this documentation/help page:
https://help.f-secure.com/product.html#home/safe-android/2016/en/concept_01B3E7B7E1FA4C6B863249AAD4217A78-safe-android-2016-en Or just direct steps view under subtopics;
Maybe with workdays there will be proper tips/advices from F-Secure team.
// later added:
Yes, sorry... I just found that "unlisted number" definitely means kind of unknown (unrecognized
numbers most likely.