Update:
I got Säästöpankki Mobile now working on Jolla phone, as Tunnistus application was replaced by SP Mobile application itself.
First updated SP Mobile in my Android phone and set it up using Androids SP Tunnistus app. (Needed several trials for some unknown reason).
Uninstalled existing SP Mobile from Jolla phone and reinstalled it from Aurora store. Set it up using new Android phone’s SP Mobiili for “tunnistus”. This managed without problems.