It's on the Izzysoft F-Droid repo: https://apt.izzysoft.de/fdroid/index/apk/eu.toldi.infinityforlemmy

The source code is found at: https://codeberg.org/Bazsalanszky/Infinity-For-Lemmy/releases

The Infinity for Lemmy sublemmy is found here: !infinityforlemmy@lemdro.id

and the developer is u/bazsalanszky@lemmy.toldi.eu

Though the name might change since its a fork and not done by the same developer: https://lemy.lol/post/2958776

I am either hoping for it to stay the same, or for it to change to Eternity.