I have used obtanium but I did not understand the benifit. It seems from what you have said that the benifit is that you get it direct from the publisher of the app. Glad to learn why it might be preferred.

For me obtainium has multiple benefits: 1. You download it from the source (when available) 2. If 1 is not possible yeah can still download it from fdroid when available there. Offcourse it would be cool if obtainium adds searching Nostr apps from the zap.store but we can only hope right 😜