Printers, Scanners & Fingerprint (Drivers & Low-level Hardware): open-source projects that exist because someone reverse engineered a closed product, sorted by GitHub stars.
Reverse-engineered Validity/Synaptics fingerprint sensor driver for ThinkPads
Prints to cheap BLE "cat" thermal printers via reverse-engineered protocol
Open driver for Brother laser printers that lack PostScript support
Open-source utility to reset Epson printer waste ink pad counters
SANE backend for driverless eSCL and WSD network scanners
Reverse-engineering tools and prototype drivers for Goodix fingerprint sensors
Enables HP All-in-One scan-to-computer without HP software
Reverse engineering the Validity 138a:0091 fingerprint sensor in Dell XPS laptops
Harness that compares vendor and Linux scanner driver USB control transfers
Open print tool for Dymo LabelManager label printers
Native Apple Silicon macOS driver for HP Laser 1003-1008 printers
libfprint driver for Elantech fingerprint sensors
Linux libfprint driver for Synaptics Tudor match-in-sensor fingerprint readers
Reverse engineering the Goodix 27c6:5395 fingerprint sensor in Dell XPS 9570
Brother printer drivers for ARM and Raspberry Pi
fprintd replacement allowing standalone backends such as python-validity
Linux program for Brother QL-570/QL-700 label printers
CUPS driver for Samsung/Xerox SPL host-based laser printers
Implementation of the MXW01 cat thermal printer BLE protocol
Brother P-Touch label printer reverse engineering and firmware work
Linux driver for the FPC 10a5:9201 fingerprint sensor controller
libfprint driver for the Goodix 27c6:5385 fingerprint sensor in the Dell XPS 13 7390
Notes and tools from reverse engineering the Goodix 5110 fingerprint reader
Web Bluetooth driver and reverse-engineered protocol docs for Niimbot label printers
Proof of concept for talking to ELAN 04f3:0c4c fingerprint readers, basis for a libfprint driver
libfprint driver for the FocalTech FT9201 (2808:93a9) USB fingerprint reader
CUPS driver for Canon CAPT v1 printers
Community hub of drivers and patches for fingerprint sensors not in libfprint
Linux driver for Dell ControlVault2 / Broadcom BCM5880 fingerprint chip
Canon LBP CAPT printer driver for Raspberry Pi CUPS
Reverse-engineered libfprint driver for EgisTec EH576 fingerprint sensor
Development of the synatlsmoc libfprint driver for Synaptics sensors
From-scratch userspace driver for Synaptics 06cb:00e7 match-on-chip sensor
Goodix fingerprint scanner SPI protocol tools
Protocol reverse engineering of the Goodix 51C0 SPI fingerprint sensor
Open fingerprint reader library with many reverse-engineered sensor drivers
Driver for Minolta magicolor 2300W/2400W/2500W host-based colour lasers
Driver for HP PPA (Printing Performance Architecture) host-based DeskJet printers
SANE scanner backends, many written from reverse-engineered scanner protocols
Driver for the UPEK/SGS Thomson fingerprint reader found in ThinkPads