I just received a Pixel 3XL as a free hand me down and need some assistance. I know it's a couple of years old but still seems to be a solid phone. I basically need to wipe this thing completely clean. The problem is that it's rooted with an unlocked bootloader with TWRP. While that might not be a huge issue it's also on a older Android version 9. I've been reading but I'm not exactly sure where to start in regards to what to do first. I know my share of rooting and flashing ROMs but my knowledge is back with the Nexus and older HTC phones. Any help would be greatly appreciated.