No, not for something that is over the network

No. You are using the APIs or scraping content.

The AGPL is meant to deal with making modifications to a GPL piece of software on a server and not releasing the source code (and changes).

For code to be GPL it needs to actually “link” in the sense of a compiler and linker, in order for it to be considered a derivative work.

Calling the REST API of AGPL software, I do not believe that meets the definition of linking.

I am not a lawyer but this is how I understand it

Ooh I’m going to have to check that out

I use Obsidian, and have the Vim bindings enabled.