Notice: When importing a number of .md Files and there is a folder inbetween, (In my case: Mac 10.15.7) Obsidian only imports the files that come alphabetically before the folder name. So when selecting the files imported from notes watch out that the folder called attachements or images is not selcted, it will stop the import at that point without noticing you.
Thank you very much for the solutions here. Exporter 3.0.6 works like charm for me. I exported more than 2.300 Notes. Failed Exports (I had 10) have been saved in a folder called “Failed Exports” and are converted to HTML. If I want their content in Obsidian I copy and paste it.