“Tailscale on a jailbroken Kindle is typically forced to run in userspace mode, which means it cannot use the device’s own network routing layer.”
A KUAL plugin puts SOCKS5 on port 1055 and HTTP CONNECT on 1056 so KOReader can reach your own Calibre or Wallabag server. It is unofficial community code and full TUN mode only works on some models, which the post says up front. The device you paid for will not talk to your own bookshelf until you jailbreak it. That is the actual story here.