After some hassle here are some simple instructions that worked for me:

1. Unlock bootloader: https://motorola-global-portal.custhelp.com/app/standalone%2Fbootloader%2Funlock-your-device-a/
2. Flash TWRP recovery from https://forum.xda-developers.com/g5/development/unofficial-twrp-3-1-0-0-moto-g5-t3574450 and boot it
3. Copy via MTP and install no-verify-opt-encrypt from https://build.nethunter.com/android-tools/no-verity-opt-encrypt/
4. Copy via MTP and install Magisk: https://forum.xda-developers.com/apps/magisk/official-magisk-v7-universal-systemless-t3473445
5. Wipe and reboot
6. Install Magisk Manager app, you should have root!

Reboot and there and it should work!

PS: SuperSU 2.79-SR4 doesn't work yet.