the Fediverse (ActivityPub) is going to be a lot gentler on the battery life of your phone than Nostr.

a client on Nostr has to do this BitTorrent kind of thing where it connects to several relays (a bit like Torrent trackers) to function.

it's a bit better suited for computer than mobile. but on a computer, in Chrome, you're looking at a lot of heat generation.

the protocol between clients and relays is WebSocket and it causes a lot of heat and fans running.

you thought Mastodon FE was bad. try any of the web clients for Nostr...