YouTuber Clemens Elflein has shared an open-source robot lawnmower project, OpenMower. The smart mower can localize and navigate using GPS rather than a perimeter wire. The gadget uses an off-the-shelf robot lawnmower, replacing the electronics with a Raspberry Pi 4, ArduSimple RTK GPS board and a Raspberry Pi Pico microcontroller.
https://www.notebookcheck.net/The-OpenMower-is-a-Raspberry-Pi-and-ArduSimple-based-robotic-lawn-mower-that-you-can-build-yourself.613269.0.html