frida-server, to be running on the device. You can download it from the frida releases page on Github - make sure you get the one ending in "android-x86".
adb push frida-server-12.8.20-android-x86 /data/local/tmp
adb root, then connect to your device with
adb shell. Navigate to the /data/local/tmp directory with
mv frida-server-12.8.20-android-x86 frida-server
chmod 777 frida-server
nohup ./frida-server &