Building on @Hook's answer: I believe the Pro1-X still always comes with official (i.e. googlified) Android, no matter what OS you ordered. You have to flash a Google-free variant yourself. Take a minute to read about the procedures and options, following the various links on that entry point he posted.
You will probably want to flash LineageOS 21. Choose between the official version without GApps or substitutes, or the derivative LineageOS-MicroG. I have always only used the former myself. For guidance, follow the very good instructions on the LineageOS wiki. Once booted, install F-Droid