[Google Pixel XL Guides, News, & Discussion] yearn2burn:
So here's my experience and tips getting SUHide to work. Acquired through a boatload of reading and sometimes painful experience.

1. Start with a good Android build. NMF26V or Pure Nexus work. There are no files yet to modify U. But NMF26V works fine even though not designed for US market and Pure Nexus files are compatible with it. I haven't tested O or Q or the older NDE63V builds, but they should work.

2. Root with SuperSU 2.79 stable release or one of the 2.78 SR releases. Definitely not a 2.79 SR release. It won't work due to SELinux handling changes. Don't forget to delete fstab.marlin during installation or you won't get root. Add a kernel like ElementalX to hide unlock bootloader.

3. Download build appropriate files to modify the lib and lib64 files. Note that there are files in the OP to modify NDE63V but not the newer NMF26V. Fortunately the Pure Nexus files from post 195 work. No files are available for U.

4. Replace the lib files. You can do this with ADB, but also entirely within TWRP. In TWRP -> Mount -> tick system. Don't tick read only. Advanced -> file manager -> /system/system/lib. There, rename libandroid_runtime.so to something else like libandroid_runtime.so.bak. Do the same at /system/system/lib64. Navigate to your modified lib files and copy them to the corresponding locations. Once placed in system, select each file with file manager -> CHMOD -> 0644.

5. Reboot to make sure you have the right lib files. If you don't, you'll just sit on the Google splash screen and never even get to the bouncing balls. If that is the case and you did above correctly, you probably don't have the right lib files for your build. You can easily go back in TWRP file manager to revert to the old files or flash the system.img in fastboot.

6. If you successfully boot, things are looking good. Download SUHide GUI from play and Rootswitch v1.3.3.2 which is a little tricky to find. Google rootswitch shakalaca 1.3.3.2. it will be first site in maybe Chinese hosted by Asus. You'll need an Asus login. Then scroll down for the download. Both SUHide GUI and rootswitch are apk files. Install both and run them to get root access. If you run them later there is a glitch with SUHide where the SuperSU prompt for root access doesn't appear.

7. TWRP flash SUHide 0.55. Google SUHide 0.55 to find the source for download. While there, download SUHide-rm 0.51. One day or another you're gonna need SUHide-rm.

8. Reboot phone. Run SUHide. Add apps you want to hide, like Android Pay and PoGo. [MENTION=522448]Fenny[/MENTION] also suggests blocking several services (post 133.)

9. To use SUHide for a particular app, first kill it by swiping it from recents. Start Rootswitch app. On means root enabled, off means root disabled. Turn it back to "on" when done.

9. If you later want to remove SUHide, TWRP flash SUHide-rm. This is necessary as SUHide doesn't install to system, but to the data partition, so reflashing firmware won't remove it. If you don't use SUHide-rm, all is fine until you try to root. You will not successfully boot and just get stuck on the bouncing balls. Easy fix once you identify the problem (read painful experience.)