UPDATE 29 Jul 19: Now confirmed working as SWD link to programme UF2 bootloader on SAMD51 at 2MHz SWD clock.
UPDATE 13 Jul 19: An unchecked dimensional drawing is available in the project images for generating other EDA package footprints. Would be great if someone can check this drawing, either against the existing kicad/eagle footprints or building in another EDA, sending to PCB fab and confirming connection with the SOIC clip.
UPDATE 17 Jun 19: The Github repo now includes an Eagle version! Please test and check it works.