TL;DR
OpenTrailPaper is an open-source project that turns the LILYGO T5 E-Paper S3 Pro development kit into a DIY e-paper bike computer. It features firmware compatible with the ESP32-S3-based T5 E-Paper devkit and includes companion apps for Android and iOS. The system displays ride data, supports offline maps, and can follow GPX (GPS Exchange Format) routes. It also records FIT (Flexible and Interoperable Data Transfer) files and connects to various Bluetooth sensors for heart rate, power, and cadence.