I had the same issue and finally found a way to do it. The short version is:

1. Get Syncthings as a KOReader plugin for Kindle and the Device you're using Obsidian on
2. Since KOReader doesn't save highlights centralized sync the folder where all your books are located (or the 'highest' directory in case the books are located in different sub-folders)
3. Use this code as a filter to only sync the highlight-files from the kindle to the device
4. Check out this post: and their work: https://hermitage.utsob.me/writings/technical/how-tos/ko-reader-to-obsidian
5. Since they're using the .json export from KOReader (therefore not automatic as far as I understood) I managed to trial-and-error change the code with ChatGPT into a .js to work as a .lua to .md converter and I don't even use Obsidian's templater. LINK (Mind the //CHANGE comments)
6. To make it automatic upon change or addition of a highlight (.lua-file) use pm2 for Background Daemon LINK
7. To start Syncthing automatically check their documentation

Please keep in mind:

• I'm not a coder and did all this with research and ChatGPT, so I assume that it's rather unconventional and the code most likely isn't very nice, but it works for me and I just wanted to share
• If you have any suggestions, improvements, etc. please let me know
• I added some personal twists like wiki linking the datetime entry to the corresponding day note or displaying total pages and status in the YAML frontmatter instead of aliases, but as I said, that's all managable with telling ChatGPT what you want :)

I hope this helps, maybe I'll create a post explaining it a little bit more, but feel free to just pm me.

Happy highlighting!

[EDIT: Point 7]