Aurora Store is way too unreliable and is nearly unusable. I have been using APKMirror so far and while it is okay, it is somewhat annoying that Obtainium can not directly download from there whereas it can with APKPure. I wanted to know the security level of APKPure in comparison to APKMirror.
F-Droid is not what many think it is. Check this out for some interesting reading.