Syncthing: https://f-droid.org/en/packages/com.github.catfriend1.syncthingandroid/
KDE Connect: https://f-droid.org/en/packages/org.kde.kdeconnect_tp/
AntennaPod: https://f-droid.org/en/packages/de.danoeh.antennapod/
DAVx⁵: https://f-droid.org/en/packages/at.bitfire.davdroid/
Obtanium: https://f-droid.org/en/packages/dev.imranr.obtainium.fdroid/
Voyager for Lemmy: https://f-droid.org/en/packages/app.vger.voyager/
Edit: Fixed link
Thank you. I am not sure how that only ended up on that link.