qalculate from KDE:Applications project
Select Your Operating System
Add repository and install manually
For KDE Frameworks5 openSUSE Leap 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:Applications/KDE_Frameworks5_openSUSE_Leap_15.5/KDE:Applications.repo zypper refresh zypper install qalculate