well sometime ago i again (after 1 year) tryed to root my phone again
What about that Hi-Res picture??
well i installed boot on as the recovery slot (to clear it) and then installed twrp
i installed it like you said it to me and its not working it just loading forever and it installed without error
Uninstall Minimal ADB and Fastboot, check if you have unlocked the bootloader and use >Google platform-tools<.
Did you ever heard of A/B slots? The Moto G6+ uses A/B slots and does not have a partition /recovery. Of course there is a recovery but it 's merged in the boot.img. So the boot.img is able to boot into recovery and also into system.
fastboot boot <TWRP.IMG>
Install Recovery Ramdiskand pick the twrp.img: