On Amethyst I can change my lightning address on the settings of my account.
Hmm, for some reason I'm not seeing it in my settings. Thanks for responding.
It's in Profile, edit icon, then here https://i.nostr.build/0jaxv.jpg
You should see something like this (my language is Italian, indirizzo LN is LN address https://image.nostr.build/5db55bde35ece6c41977bfc2f0a08749b33d6c2ef774eac3d9252fb28f87daa6.jpg )