Information for wallet developers

Hello! I’m a non-custodial wallet developer.
Our users are eager to get their Glacier Drop.

I see there is a manual way to sign a message, which can be the easiest way for us.
But is there some documentation on how to sign? For example, messages to sign are usually prefixed with “Ethereum signed message” in EVM. Is it like this in our case? And what’s with other networks?
And I was told there is some API we can use for a more streamlined flow. Can you share a link to it?

We have a chat with developers for 2 weeks already, but they couldn’t be less useful, they provided exactly 0 info on the issue, except that there IS some API. This is no way to launch a decentralized system, this all should be a part of the public documentation, not be hidden somewhere.
The time is ticking, the deadline is quite tight for us to push an update.