dikaios1517 on Nostr: Amber can do entirely local signing using NIP-55, but it also supports remote signing ...

Amber can do entirely local signing using NIP-55, but it also supports remote signing via NIP-46. It uses relays to transfer the unsigned data to Amber, then the data is signed locally and transferred back to the client via relays. The relays used can be selected by the user and can even use a local relay, such as Citrine.

That said, even using Amber for NIP-46 signing has been spotty for me. Not sure why. It is using a similar concept as Nostr Wallet Connect, which has always worked quite well, but remote signing often just fails for some reason.