Do you have any more information about this?
I haven’t personally setup Tailscale yet, but looking at this it seems possible and not too difficult https://github.com/videah/kobo-tailscale
install Tailscale on your Kobo
install Koreader
Install Tailscale on the machine that host your eBook collection app of choice
Add the OPDS URL from the collection app, replacing the local machine URL with the Tailscale URL
You can now browse and download your private collection from anywhere.
I went with Kavita since I wanted my eBooks treated as equals with my manga.