thanks to you guys!
Just want to share my experience: Since I had to learn that the Mac version of OneNote doesn’t offer any useful export option, I went the Obsidian route which worked like a charm.
The only thing to note is that the actual notes were nested in a folder/group structure as they were organized in OneNote, while the attached images ended up in the topmost folder of the import.
This I could resolve by search/replace (something like search “(Exported” / replace “(/myTopFolder/Exported”).
If you do not want to have all assets of all notebooks mixed up in one folder, you will need do import one notebook at a time, then moving the images and search/replace the links as needed.