also do classes as in manpage, no double escapes needed
[Service]
Type=simple
-ExecStart=sh -c "stdbuf -oL libinput debug-events | egrep --line-buffered '^[[:space:]-]+event[0-9]+\\s+SWITCH_TOGGLE\\s' | while read line; do autorandr --batch --change --default default; done"
+ExecStart=sh -c "stdbuf -oL libinput debug-events | grep -E --line-buffered '^[[:space:]-]+event[0-9]+[[:space:]]+SWITCH_TOGGLE[[:space:]]' | while read line; do autorandr --batch --change --default default; done"
Restart=always
RestartSec=30
SyslogIdentifier=autorandr