Root Fairphone 3

fp3root.sh

#!/bin/sh
FASTBOOT=fastboot
ADB=adb
MAGISK=v20.3
TWRP_RELEASE=20200202-02
TWRP=3.3.1-0_k4y0z-${TWRP_RELEASE}-fp3
mkdir -p /tmp/flash_fp3_${TWRP_RELEASE}
cd /tmp/flash_fp3_${TWRP_RELEASE}/

wget -nc https://github.com/chaosmaster/android_device_fairphone_fp3/releases/download/${TWRP_RELEASE}/twrp-${TWRP}.img
wget -nc https://github.com/chaosmaster/android_device_fairphone_fp3/releases/download/${TWRP_RELEASE}/twrp-installer-${TWRP}.zip
wget -nc https://github.com/topjohnwu/Magisk/releases/download/${MAGISK}/Magisk-${MAGISK}.zip

${ADB} reboot bootloader

product=$(${FASTBOOT} getvar product 2>&1 | grep -oE 'product:\s+FP3')
if [ $? -ne 0 ]; then
    echo "This device is not a Fairphone 3!"
    ${FASTBOOT} continue
    exit 1
fi

${FASTBOOT} boot ./twrp-${TWRP}.img
${ADB} wait-for-recovery && ${ADB} shell twrp sideload && ${ADB} wait-for-sideload && ${ADB} sideload twrp-installer-${TWRP}.zip
${ADB} wait-for-recovery && ${ADB} shell twrp sideload && ${ADB} wait-for-sideload && ${ADB} sideload Magisk-${MAGISK}.zip
echo "Flashed TWRP and Magisk"
echo "Rebooting to device..."
${ADB} wait-for-recovery && ${ADB} reboot

Great Script !!!
I just changed to line
MAGISK=v20.3
to
MAGISK=v21.2

Works like a charm.