Since the new driver for the official Raspberry Pi touchscreen was introduced with this patch the touchscreen no longer reports as "FT5406 memory based driver" but as "raspberrypi-ts" instead. To add support for this new driver I suggest adding these lines into the raspberry pi touchscreen rules into rules/70-touchscreen-raspberrypi.rules
# add support for raspberrypi-ts driver introduced by kernel 4.21
ACTION=="add",KERNEL=="event*",ATTRS{name}=="raspberrypi-ts",SYMLINK+="twofingtouch",MODE="0440"
KERNEL=="event*",ATTRS{name}=="raspberrypi-ts",SYMLINK+="twofingtouch",MODE="0440"
Since the new driver for the official Raspberry Pi touchscreen was introduced with this patch the touchscreen no longer reports as "FT5406 memory based driver" but as "raspberrypi-ts" instead. To add support for this new driver I suggest adding these lines into the raspberry pi touchscreen rules into
rules/70-touchscreen-raspberrypi.rules
or creating a new file with these rules.