How convert a sdk Android / IOS in capacitor plugin

I have an Ionic 5 app with capacitor/angular, deployed on android or ios.

I need to embed a feature that requires calling functions from an android/ios proprietary sdk.
This SDK is a black box for me.

I don’t see how I can use it in the IONIC app, where currently the plugins are only imported with NPM.
I don’t know if I can convert an sdk to an npm plugin, or if there is another way.

Anyone have any advice on the possibilities ?

You can’t convert an existing SDK into a plugin, you can create a plugin that uses a SDK.

But if you say that the SDK is a black box to you, not sure how you can use it.

It’s a black box in the sense that I can’t look at its code or modify it. But I know its API.

Do you have a link that explains how to do this? I must not have the right words, I can’t find a tutorial.