Guys!
First, I got to say that it's true when those all those guys have written
TWRP 3.1.1-0 doesn't work for everyone if after reinstall the original firmware they've tried to flash TWRP again. It says "not signed or corrupted" and if they attempt, from bootloader, to go to recovery mode, the cellphone shows an android logo and then "no command". The solution I've found after reading all this thread has been flashing the modified
TWRP vR16 (
https://xdaforums.com/moto-g5s-plus/development/recovery-twrp-3-1-1-r7-t3694910). It will show you the same "bug", but now you'll be able to access to recovery mode.
Finally, I've rooted my XT1801 (Latam version) with Magisk and now I'm working on how to figure out the installation of Viper and Xposed on stock rom.
I'm not a developer, but if someone still has problems with it, I'll be glad to help.