Install Android support via Jolla store.
Potentially reboot after the installation of Android support completed. With Uitukka (18.104.22.168) my Jolla seemed to need the reboot. (FIXME: citation needed, search Together.Jolla.Com for this.)
Grab the file for a custom Android without com.google.android.maps library (aosp) from Öffi’s download page.
Öffi should be on your app screen now.
It works fine for me. But is is important to understand that, if you do not have the Google stuff, Öffi can of course not show you maps. That’s absolutely fine by me.