Interesting - didnt hear about Jolla phones before this but found that they use Sailfish OS:

"Sailfish OS has the in-built capability to run Android™ apps on your Jolla. So you can continue using your favourite apps like Instagram, Facebook, WhatsApp and Twitter as well as downloading all the latest ones via the Yandex and Aptoide Stores and other Android™ marketplaces."

As the Clef app is on Android, it would appear to work on Jolla - curious about this, please post here if this works for you