I have found Obtainium to be quite unreliable and am surprised by how many people recommend it.
In my case it frequently fails to detect which version I have installed, fails to detect there is a new version, and even tells me an app is outdated when the version I have installed is higher than what it believes is the highest version. I currently use it only for 2 apps: Uazo’s Chromium build (which is not on F-Droid) and Obtainium itself.
In case an app is on F-Droid I personally see no reason to get/update it through Obtainium.