Tachiyomi, but honestly I mostly use Neko which is a fork of TachiyomiJ2K which is a fork of Tachiyomi. Both aren’t on Fdroid but at least they are completely FOSS.
It’s the best Manga reader out there and it supports basically every Manga website out there and more.
DNS66 is an amazing adblocker
LibreTube is the best youtube client out there
Many apps that are on F-Droid are also on Google Play, but there are exceptions. Gadgetbridge (smart watch connection app) warns that the Google Play version is unofficial and unaffiliated. An unofficial app might be upstream compiled without modifications, but this opens users to potential supply chain attacks from the uploader and Google.
F-droid is great. But I wish f-droid had some kind of rating system so that I could use it more.
NewPipe
Simple calendar
Simple gallery
SD Maid
KeePassDX
MuPDF mini
Open contacts
OsmAnd~
Slight backup
VLC
Jerboa
F-droid
ps: how do you make a list on Jerboa/lemmy?