This is what I'm currently doing sans tailscale. I'm running Ubooquity on a server in my homelab as my OPDS service to serve the ebooks hosted on a mounted NAS. I can download any of those books from my Kobo with a few presses on Koreader. It's pretty great. My Kobo Forma is probably one of my best and most used tech purchases. I've had it since 2019 and couldn't be happier with the device + setup. Getting it set up with tailscale so I can fetch ebooks when I'm away from home sounds like a pretty good upgrade.