evtest output of first pressing backslash/pipe key (lower left corner) and then hash/tilde key (just left of return), with pristine udev:
Event: time 1536705976.250768, type 4 (EV_MSC), code 4 (MSC_SCAN), value 56 Event: time 1536705976.250768, type 1 (EV_KEY), code 43 (KEY_BACKSLASH), value 1 Event: time 1536705976.250768, -------------- SYN_REPORT ------------ 'Event: time 1536705976.367113, type 4 (EV_MSC), code 4 (MSC_SCAN), value 56 Event: time 1536705976.367113, type 1 (EV_KEY), code 43 (KEY_BACKSLASH), value 0 Event: time 1536705976.367113, -------------- SYN_REPORT ------------ Event: time 1536705984.751884, type 4 (EV_MSC), code 4 (MSC_SCAN), value 2b Event: time 1536705984.751884, type 1 (EV_KEY), code 43 (KEY_BACKSLASH), value 1 Event: time 1536705984.751884, -------------- SYN_REPORT ------------ 'Event: time 1536705984.868556, type 4 (EV_MSC), code 4 (MSC_SCAN), value 2b Event: time 1536705984.868556, type 1 (EV_KEY), code 43 (KEY_BACKSLASH), value 0 Event: time 1536705984.868556, -------------- SYN_REPORT ------------