tl;dr: Community developers have improved Tailscale support on jailbroken Kindles, adding SSH-by-default, a SOCKS5/HTTP CONNECT proxy mode so apps like KOReader can reach tailnet services (Calibre, Wallabag, Audiobookshelf), and full TUN mode on some devices. A separate KOReader plugin brings the same proxy functionality to Kobo and PocketBook readers, though it doesn't expose the device on your tailnet. Setup requires copying files, installing via KUAL or KOReader's menu, and pointing apps at 127.0.0.1:1055/1056.