Readwise offers export of highlights to markdown files. I tested this today and the files really look excellent under Obsidian. Once downloaded and added to the vault by moving it to the folder (I use Hazel for this so that it is done automatically) it shows up well within Obsidian.
The Readwise zip arrives in my download folder, it then runs the Hazel workflow. I have created an inbox in Obsidian for files that come from outside. The files arrive in the inbox in a Readwise folder. I then process is it from within Obsidian however I want it.