Obtainium doesn't even come close to fdroid . like it isn't even a question bruh completely different things as one is just a tool to make updates easy the other is a high privacy and security app store with really good policy, security and privacy check etc.
One reason I'm thankful for Obtainium is because "OAuth was not approved by Google, etc for the F-Droid build" of Fair Email, and unfortunately, that's still important for me.
Obtainium is able to download from the official F-droid repo too.
I wasn't comparing the two but you go ahead and do you, I prefer finding apps on my own and just getting them direct from the devs. Damn people are defensive as fuck around here, shit.
Who knows if there isn't some fundamental and simple flaw with some part of it that nobody is seeing. For what worth the all Snowden could be a major psy-op to make people believe that Signal is really secure and that there are no backdoors into it - after all the guy spends most of the time promoting Signal.